diff --git a/CMakeLists.txt b/CMakeLists.txt
index cfefc6982e..1a651ed6a8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,7 +37,7 @@ SET(PACKAGE_VERSION ${VERSION})
 
 # Version of the dispatch table. This must match the value in
 # configure.ac.
-SET(NC_DISPATCH_VERSION 3)
+SET(NC_DISPATCH_VERSION 4)
 
 # Get system configuration, Use it to determine osname, os release, cpu. These
 # will be used when committing to CDash.
@@ -1404,6 +1404,9 @@ ENDIF()
 # Always enable DISKLESS
 OPTION(ENABLE_DISKLESS "Enable in-memory files" ON)
 
+# Always enable quantization.
+OPTION(ENABLE_QUANTIZE "Enable variable quantization" ON)
+
 # By default, MSVC has a stack size of 1000000.
 # Allow a user to override this.
 IF(MSVC)
@@ -2180,6 +2183,7 @@ is_enabled(ENABLE_NCZARR HAS_NCZARR)
 is_enabled(ENABLE_NCZARR_S3_TESTS DO_NCZARR_S3_TESTS)
 is_enabled(ENABLE_MULTIFILTERS HAS_MULTIFILTERS)
 is_enabled(ENABLE_NCZARR_ZIP DO_NCZARR_ZIP_TESTS)
+is_enabled(ENABLE_QUANTIZE HAS_QUANTIZE)
 
 # Generate file from template.
 CONFIGURE_FILE("${CMAKE_CURRENT_SOURCE_DIR}/libnetcdf.settings.in"
diff --git a/configure.ac b/configure.ac
index a3e88630e0..60099c74e9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1649,6 +1649,7 @@ AC_SUBST(HAS_NCZARR,[$enable_nczarr])
 AC_SUBST(DO_NCZARR_S3_TESTS,[$enable_nczarr_s3_tests])
 AC_SUBST(HAS_MULTIFILTERS,[$has_multifilters])
 AC_SUBST(DO_NCZARR_ZIP_TESTS,[$enable_nczarr_zip])
+AC_SUBST([HAS_QUANTIZE],[yes])
 
 # Include some specifics for netcdf on windows.
 #AH_VERBATIM([_WIN32_STRICMP],
@@ -1728,7 +1729,7 @@ AX_SET_META([NC_HAS_MULTIFILTERS],[$has_multifilters],[yes])
 # dispatch table to submit. If this is changed, make sure the value in
 # CMakeLists.txt also changes to match.
 
-AC_SUBST([NC_DISPATCH_VERSION], [3])
+AC_SUBST([NC_DISPATCH_VERSION], [4])
 AC_DEFINE_UNQUOTED([NC_DISPATCH_VERSION], [${NC_DISPATCH_VERSION}], [Dispatch table version.])
 
 #####
diff --git a/include/hdf5dispatch.h b/include/hdf5dispatch.h
index 1e57eb1e90..cb41cb9fa1 100644
--- a/include/hdf5dispatch.h
+++ b/include/hdf5dispatch.h
@@ -47,7 +47,8 @@ extern "C" {
                          int *shufflep, int *deflatep, int *deflate_levelp,
                          int *fletcher32p, int *contiguousp, size_t *chunksizesp,
                          int *no_fill, void *fill_valuep, int *endiannessp,
-                         unsigned int *idp, size_t *nparamsp, unsigned int *params);
+                         unsigned int *idp, size_t *nparamsp, unsigned int *params,
+			 int *quantize_modep, int *nsdp);
 
     EXTERNL int
     NC4_HDF5_set_var_chunk_cache(int ncid, int varid, size_t size, size_t nelems,
diff --git a/include/hdf5internal.h b/include/hdf5internal.h
index cbb8526356..c35c1173a7 100644
--- a/include/hdf5internal.h
+++ b/include/hdf5internal.h
@@ -200,6 +200,10 @@ int NC4_hdf5_addfilter(NC_VAR_INFO_T* var, unsigned int id, size_t nparams, cons
 int NC4_hdf5_filter_freelist(NC_VAR_INFO_T* var);
 int NC4_hdf5_find_missing_filter(NC_VAR_INFO_T* var, unsigned int* idp);
 
+/* Add an attribute to the attribute list. */
+int nc4_put_att(NC_GRP_INFO_T* grp, int varid, const char *name, nc_type file_type,
+		size_t len, const void *data, nc_type mem_type, int force);
+
 /* Support functions for provenance info (defined in nc4hdf.c) */
 extern int NC4_hdf5get_libversion(unsigned*,unsigned*,unsigned*);/*libsrc4/nc4hdf.c*/
 extern int NC4_hdf5get_superblock(struct NC_FILE_INFO*, int*);/*libsrc4/nc4hdf.c*/
diff --git a/include/nc4dispatch.h b/include/nc4dispatch.h
index 16d9ebd78d..04bd4ca267 100644
--- a/include/nc4dispatch.h
+++ b/include/nc4dispatch.h
@@ -101,7 +101,8 @@ extern "C" {
                     int *shufflep, int *deflatep, int *deflate_levelp,
                     int *fletcher32p, int *contiguousp, size_t *chunksizesp,
                     int *no_fill, void *fill_valuep, int *endiannessp,
-                    unsigned int* idp, size_t* nparamsp, unsigned int* params);
+                    unsigned int* idp, size_t* nparamsp, unsigned int* params,
+		    int *quantize_modep, int *nsdp);
 
     EXTERNL int
     NC4_inq_varid(int ncid, const char *name, int *varidp);
@@ -251,6 +252,13 @@ extern "C" {
     EXTERNL int
     NC4_inq_var_filter_info(int ncid, int varid, unsigned int id, size_t* nparams, unsigned int* params);
 
+    EXTERNL int
+    NC4_def_var_quantize(int ncid, int varid, int quantize_mode, int nsd);
+
+    EXTERNL int
+    NC4_inq_var_quantize(int ncid, int varid, int *quantize_modep, int *nsdp);
+    
+
 #if defined(__cplusplus)
 }
 #endif
diff --git a/include/nc4internal.h b/include/nc4internal.h
index 49bda44f1c..e2686c0e92 100644
--- a/include/nc4internal.h
+++ b/include/nc4internal.h
@@ -204,6 +204,8 @@ typedef struct NC_VAR_INFO
     size_t chunk_cache_size;     /**< Size in bytes of the var chunk chache. */
     size_t chunk_cache_nelems;   /**< Number of slots in var chunk cache. */
     float chunk_cache_preemption; /**< Chunk cache preemtion policy. */
+    int quantize_mode;           /**< Quantize mode. NC_NOQUANTIZE is 0, and means no quantization. */
+    int nsd;                     /**< Number of significant digits if quantization is used, 0 if not. */
     void *format_var_info;       /**< Pointer to any binary format info. */
     void* filters;             /**< Record of the list of filters to be applied to var data; format dependent */
 } NC_VAR_INFO_T;
diff --git a/include/ncdispatch.h b/include/ncdispatch.h
index 2626036738..8ce09a8d06 100644
--- a/include/ncdispatch.h
+++ b/include/ncdispatch.h
@@ -249,7 +249,8 @@ NCDISPATCH_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
                int *shufflep, int *deflatep, int *deflate_levelp,
                int *fletcher32p, int *contiguousp, size_t *chunksizesp,
                int *no_fill, void *fill_valuep, int *endiannessp,
-	       unsigned int* idp, size_t* nparamsp, unsigned int* paramsp
+	       unsigned int* idp, size_t* nparamsp, unsigned int* paramsp,
+	       int *quantize_modep, int *nsdp
                );
 EXTERNL int
 NCDISPATCH_get_att(int ncid, int varid, const char* name, void* value, nc_type t);
diff --git a/include/netcdf.h b/include/netcdf.h
index 3af038e3ed..c3ff2f5d0f 100644
--- a/include/netcdf.h
+++ b/include/netcdf.h
@@ -324,6 +324,13 @@ there. */
 #define NC_MIN_DEFLATE_LEVEL 0 /**< Minimum deflate level. */
 #define NC_MAX_DEFLATE_LEVEL 9 /**< Maximum deflate level. */
 
+#define NC_NOQUANTIZE 0 /**< No quantization in use. */    
+#define NC_QUANTIZE_BITGROOM 1 /**< Use bitgroom quantization. */
+
+/** When quantization is used for a variable, an attribute of this
+ * name is added. */
+#define NC_QUANTIZE_ATT_NAME "number_of_significant_digits" 
+
 /** The netcdf version 3 functions all return integer error status.
  * These are the possible values, in addition to certain values from
  * the system errno.h.
@@ -854,6 +861,16 @@ nc_get_varm(int ncid, int varid,  const size_t *startp,
 
 /* Extra netcdf-4 stuff. */
 
+/* Set quantization settings for a variable. Quantizing data improves
+ * later compression. Must be called after nc_def_var and before
+ * nc_enddef. */
+EXTERNL int
+nc_def_var_quantize(int ncid, int varid, int quantize_mode, int nsd);
+
+/* Find out quantization settings of a var. */
+EXTERNL int
+nc_inq_var_quantize(int ncid, int varid, int *quantize_modep, int *nsdp);
+
 /* Set compression settings for a variable. Lower is faster, higher is
  * better. Must be called after nc_def_var and before nc_enddef. */
 EXTERNL int
diff --git a/include/netcdf_dispatch.h.in b/include/netcdf_dispatch.h.in
index 9b90cc3424..4f9f59b729 100644
--- a/include/netcdf_dispatch.h.in
+++ b/include/netcdf_dispatch.h.in
@@ -93,7 +93,7 @@ struct NC_Dispatch
                        int *fletcher32p, int *contiguousp, size_t *chunksizesp,
                        int *no_fill, void *fill_valuep, int *endiannessp,
                        unsigned int *idp, size_t *nparamsp,
-                       unsigned int *params);
+                       unsigned int *params, int *quantize_modep, int *nsdp);
 
     int (*var_par_access)(int, int, int);
     int (*def_var_fill)(int, int, int, const void *);
@@ -147,6 +147,7 @@ struct NC_Dispatch
     /* Version 3 Replace filteractions with more specific functions */
     int (*inq_var_filter_ids)(int ncid, int varid, size_t* nfilters, unsigned int* filterids);
     int (*inq_var_filter_info)(int ncid, int varid, unsigned int id, size_t* nparams, unsigned int* params);
+    int (*def_var_quantize)(int ncid, int varid, int quantize_mode, int nsd);
 };
 
 #if defined(__cplusplus)
@@ -223,6 +224,7 @@ extern "C" {
     EXTERNL int NC_NOTNC4_inq_typeids(int, int *, int *);
     EXTERNL int NC_NOTNC4_inq_user_type(int, nc_type, char *, size_t *,
                                         nc_type *, size_t *, int *);
+    EXTERNL int NC_NOTNC4_def_var_quantize(int, int,  int, int);
 
     /* These functions are for dispatch layers that don't implement
      * the enhanced model, but want to succeed anyway.
diff --git a/include/netcdf_meta.h.in b/include/netcdf_meta.h.in
index 340d53f74b..ce243c5d4c 100644
--- a/include/netcdf_meta.h.in
+++ b/include/netcdf_meta.h.in
@@ -62,5 +62,6 @@
 #define NC_HAS_PAR_FILTERS @NC_HAS_PAR_FILTERS@ /* Parallel I/O with filter support. */
 #define NC_HAS_NCZARR      @NC_HAS_NCZARR@
 #define NC_HAS_MULTIFILTERS   @NC_HAS_MULTIFILTERS@
+#define NC_HAS_QUANTIZE    @NC_HAS_QUANTIZE@
 
 #endif
diff --git a/libdap2/ncd2dispatch.c b/libdap2/ncd2dispatch.c
index d34ee4fa46..ffd506d64f 100644
--- a/libdap2/ncd2dispatch.c
+++ b/libdap2/ncd2dispatch.c
@@ -178,6 +178,7 @@ NCD2_get_var_chunk_cache,
 NC_NOOP_inq_var_filter_ids,
 NC_NOOP_inq_var_filter_info,
 
+NC_NOTNC4_def_var_quantize,
 };
 
 const NC_Dispatch* NCD2_dispatch_table = NULL; /* moved here from ddispatch.c */
@@ -2441,8 +2442,9 @@ NCD2_inq_var_all(int ncid, int varid, char *name, nc_type* xtypep,
                int* shufflep, int* deflatep, int* deflate_levelp,
                int* fletcher32p, int* contiguousp, size_t* chunksizesp,
                int* no_fill, void* fill_valuep, int* endiannessp,
-	       unsigned int* idp, size_t* nparamsp, unsigned int* params
-               )
+		 unsigned int* idp, size_t* nparamsp, unsigned int* params,
+		 int *quantize_modep, int *nsdp
+    )
 {
     NC* drno;
     int ret;
@@ -2452,7 +2454,7 @@ NCD2_inq_var_all(int ncid, int varid, char *name, nc_type* xtypep,
                shufflep, deflatep, deflate_levelp,
                fletcher32p, contiguousp, chunksizesp,
                no_fill, fill_valuep, endiannessp,
-	       idp,nparamsp,params
+               idp,nparamsp,params,quantize_modep, nsdp
 	       );
     return THROW(ret);
 }
diff --git a/libdap2/ncd2dispatch.h b/libdap2/ncd2dispatch.h
index 03bb10140a..dd1c01748b 100644
--- a/libdap2/ncd2dispatch.h
+++ b/libdap2/ncd2dispatch.h
@@ -124,21 +124,23 @@ NCD2_def_var(int ncid, const char *name,
 
 extern int
 NCD2_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
-             int *ndimsp, int *dimidsp, int *nattsp,
-             int *shufflep, int *deflatep, int *deflate_levelp,
-             int *fletcher32p, int *contiguousp, size_t *chunksizesp,
-             int *no_fill, void *fill_valuep, int *endiannessp,
-	       unsigned int* idp, size_t* nparamsp, unsigned int* params
-             );
+		 int *ndimsp, int *dimidsp, int *nattsp,
+		 int *shufflep, int *deflatep, int *deflate_levelp,
+		 int *fletcher32p, int *contiguousp, size_t *chunksizesp,
+		 int *no_fill, void *fill_valuep, int *endiannessp,
+		 unsigned int* idp, size_t* nparamsp, unsigned int* params,
+		 int *quantize_modep, int *nsdp
+    );
 
 extern int
 NC3_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
-             int *ndimsp, int *dimidsp, int *nattsp,
-             int *shufflep, int *deflatep, int *deflate_levelp,
-             int *fletcher32p, int *contiguousp, size_t *chunksizesp,
-             int *no_fill, void *fill_valuep, int *endiannessp,
-	       unsigned int* idp, size_t* nparamsp, unsigned int* params
-             );
+		int *ndimsp, int *dimidsp, int *nattsp,
+		int *shufflep, int *deflatep, int *deflate_levelp,
+		int *fletcher32p, int *contiguousp, size_t *chunksizesp,
+		int *no_fill, void *fill_valuep, int *endiannessp,
+		unsigned int* idp, size_t* nparamsp, unsigned int* params,
+		int *quantize_modep, int *nsdp		
+    );
 
 extern int
 NCD2_inq_varid(int ncid, const char *name, int *varidp);
diff --git a/libdap4/ncd4dispatch.c b/libdap4/ncd4dispatch.c
index 3f887a7e76..a0b3db69c8 100644
--- a/libdap4/ncd4dispatch.c
+++ b/libdap4/ncd4dispatch.c
@@ -456,8 +456,9 @@ NCD4_inq_var_all(int ncid, int varid, char *name, nc_type* xtypep,
                int* shufflep, int* deflatep, int* deflate_levelp,
                int* fletcher32p, int* contiguousp, size_t* chunksizesp,
                int* no_fill, void* fill_valuep, int* endiannessp,
-	       unsigned int* idp, size_t* nparamsp, unsigned int* params
-               )
+		 unsigned int* idp, size_t* nparamsp, unsigned int* params,
+		 int *quantize_modep, int *nsdp
+    )
 {
     NC* ncp;
     int ret;
@@ -469,7 +470,7 @@ NCD4_inq_var_all(int ncid, int varid, char *name, nc_type* xtypep,
                shufflep, deflatep, deflate_levelp,
                fletcher32p, contiguousp, chunksizesp,
                no_fill, fill_valuep, endiannessp,
-               idp, nparamsp, params);
+		 idp, nparamsp, params, quantize_modep, nsdp);
     return (ret);
 }
 
@@ -974,4 +975,5 @@ NCD4_get_var_chunk_cache,
 
 NC_NOTNC4_inq_var_filter_ids,
 NC_NOTNC4_inq_var_filter_info,
+NC_NOTNC4_def_var_quantize,
 };
diff --git a/libdispatch/dinternal.c b/libdispatch/dinternal.c
index c94e2f3ccc..b4084c5b21 100644
--- a/libdispatch/dinternal.c
+++ b/libdispatch/dinternal.c
@@ -16,12 +16,12 @@ in libdap2.
 
 int
 NCDISPATCH_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
-               int *ndimsp, int *dimidsp, int *nattsp,
-               int *shufflep, int *deflatep, int *deflate_levelp,
-               int *fletcher32p, int *contiguousp, size_t *chunksizesp,
-               int *no_fill, void *fill_valuep, int *endiannessp,
-	       unsigned int* idp, size_t* nparamsp, unsigned int* params
-               )
+		       int *ndimsp, int *dimidsp, int *nattsp,
+		       int *shufflep, int *deflatep, int *deflate_levelp,
+		       int *fletcher32p, int *contiguousp, size_t *chunksizesp,
+		       int *no_fill, void *fill_valuep, int *endiannessp,
+		       unsigned int* idp, size_t* nparamsp, unsigned int* params,
+		       int *quantize_modep, int *nsdp)
 {
    NC* ncp;
    int stat = NC_check_id(ncid,&ncp);
@@ -33,7 +33,7 @@ NCDISPATCH_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
       contiguousp, chunksizesp,
       no_fill, fill_valuep,
       endiannessp,
-      idp, nparamsp, params);
+      idp, nparamsp, params, quantize_modep, nsdp);
 }
 
 int
diff --git a/libdispatch/dnotnc4.c b/libdispatch/dnotnc4.c
index 2adba6e11e..4deed435bc 100644
--- a/libdispatch/dnotnc4.c
+++ b/libdispatch/dnotnc4.c
@@ -19,6 +19,23 @@
 #include "ncdispatch.h"
 #include "nc4internal.h"
 
+/**
+ * @internal Not implemented in some dispatch tables
+ *
+ * @param ncid Ignored.
+ * @param varid Ignored.
+ * @param quantize_mode Ignored.
+ * @param nsd Ignored.
+ *
+ * @return ::NC_ENOTNC4 Not implemented for a dispatch table
+ * @author Ed Hartnett
+ */
+int
+NC_NOTNC4_def_var_quantize(int ncid, int varid,  int quantize_mode, int nsd)
+{
+    return NC_ENOTNC4;
+}
+
 /**
  * @internal Not implemented in some dispatch tables
  *
diff --git a/libdispatch/dvar.c b/libdispatch/dvar.c
index 95859d2e38..4dfc903cc4 100644
--- a/libdispatch/dvar.c
+++ b/libdispatch/dvar.c
@@ -461,6 +461,69 @@ nc_def_var_deflate(int ncid, int varid, int shuffle, int deflate, int deflate_le
     return ncp->dispatch->def_var_deflate(ncid,varid,shuffle,deflate,deflate_level);
 }
 
+/**
+   Turn on quantization for a variable.
+  
+   The data data are quantized by setting unneeded bits alternately to
+   1/0, so that they may compress well. Quantization is lossy (data
+   are irretrievably altered), and it improves the compression ratio
+   provided by a subsequent lossless compression filter. Quantization
+   alone will not reduce the size of the data - lossless compression
+   like zlib must also be used (see nc_def_var_deflate()).
+
+   This data quantization used the bitgroom algorithm. A notable
+   feature of BitGroom is that the data it processes remain in IEEE754
+   format after quantization. Therefore the BitGroom algorithm does
+   nothing when data are read.
+  
+   Quantization is only available for variables of type NC_FLOAT or
+   NC_DOUBLE. Attempts to set quantization for other variable
+   types return an error (NC_EINVAL). 
+
+   Quantization is not applied to values equal to the value of the
+   _FillValue attribute, if any. 
+
+   For more information about quantization and the bitgroom filter, see 
+
+   Zender, C. S. (2016), Bit Grooming: Statistically accurate
+   precision-preserving quantization with compression, evaluated in
+   the netCDF Operators (NCO, v4.4.8+), Geosci. Model Dev., 9,
+   3199-3211, doi:10.5194/gmd-9-3199-2016 Retrieved on Sep 21, 2020
+   from
+   https://www.researchgate.net/publication/301575383_Bit_Grooming_Statistically_accurate_precision-preserving_quantization_with_compression_evaluated_in_the_netCDF_Operators_NCO_v448.
+  
+   @param ncid File ID.
+   @param varid Variable ID. NC_GLOBAL is not a valid varid, and may
+   not be used.
+   @param quantize_mode A integer flag specifying the quantization
+   used. Current NC_QUANTIZE_BITGROOM is the only available setting.
+   @param nsd Number of significant digits to retain. Allowed single- and
+   double-precision NSDs are 1-7 and 1-15, respectively.
+  
+   @return ::NC_NOERR No error.
+   @return ::NC_EGLOBAL Can't use ::NC_GLOBAL with this function.
+   @return ::NC_EBADID Bad ncid.
+   @return ::NC_ENOTVAR Invalid variable ID.
+   @return ::NC_ENOTNC4 Attempting netcdf-4 operation on file that is
+   not netCDF-4/HDF5.
+   @return ::NC_ESTRICTNC3 Attempting netcdf-4 operation on strict nc3
+   netcdf-4 file.
+   @return ::NC_ELATEDEF Too late to change settings for this variable.
+   @return ::NC_EINVAL Invalid input
+   @author Charlie Zender, Ed Hartnett
+ */
+int
+nc_def_var_quantize(int ncid, int varid, int quantize_mode, int nsd)
+{
+    NC* ncp;
+    int stat = NC_check_id(ncid,&ncp);
+    if(stat != NC_NOERR) return stat;
+
+    /* Using NC_GLOBAL is illegal. */
+    if (varid == NC_GLOBAL) return NC_EGLOBAL;
+    return ncp->dispatch->def_var_quantize(ncid,varid,quantize_mode,nsd);
+}
+
 /**
    Set checksum for a var.
 
diff --git a/libdispatch/dvarinq.c b/libdispatch/dvarinq.c
index 1684c57dbc..a5900317f3 100644
--- a/libdispatch/dvarinq.c
+++ b/libdispatch/dvarinq.c
@@ -131,7 +131,7 @@ nc_inq_var(int ncid, int varid, char *name, nc_type *xtypep,
    return ncp->dispatch->inq_var_all(ncid, varid, name, xtypep, ndimsp,
 				     dimidsp, nattsp, NULL, NULL, NULL,
 				     NULL, NULL, NULL, NULL, NULL, NULL,
-				     NULL,NULL,NULL);
+				     NULL, NULL, NULL, NULL, NULL);
 }
 
 /**
@@ -350,7 +350,11 @@ nc_inq_var_deflate(int ncid, int varid, int *shufflep, int *deflatep, int *defla
       NULL, /*nofillp*/
       NULL, /*fillvaluep*/
       NULL, /*endianp*/
-      NULL, NULL, NULL
+      NULL, /* idp */
+      NULL, /* nparamsp */
+      NULL, /* params */
+      NULL, /* quantize_modep */
+      NULL /* nsdp */
       );
 }
 
@@ -397,7 +401,11 @@ nc_inq_var_fletcher32(int ncid, int varid, int *fletcher32p)
       NULL, /*nofillp*/
       NULL, /*fillvaluep*/
       NULL, /*endianp*/
-      NULL, NULL, NULL
+      NULL, /* idp */
+      NULL, /* nparamsp */
+      NULL, /* params */
+      NULL, /* quantize_modep */
+      NULL /* nsdp */
       );
 }
 
@@ -472,7 +480,7 @@ nc_inq_var_chunking(int ncid, int varid, int *storagep, size_t *chunksizesp)
    return ncp->dispatch->inq_var_all(ncid, varid, NULL, NULL, NULL, NULL,
 				     NULL, NULL, NULL, NULL, NULL, storagep,
 				     chunksizesp, NULL, NULL, NULL,
-                                     NULL, NULL, NULL);
+                                     NULL, NULL, NULL, NULL, NULL);
 }
 
 /** \ingroup variables
@@ -523,10 +531,63 @@ nc_inq_var_fill(int ncid, int varid, int *no_fill, void *fill_valuep)
       no_fill, /*nofillp*/
       fill_valuep, /*fillvaluep*/
       NULL, /*endianp*/
-      NULL, NULL, NULL
+      NULL, /* idp */
+      NULL, /* nparamsp */
+      NULL, /* params */
+      NULL, /* quantize_modep */
+      NULL /* nsdp */
       );
 }
 
+/** @ingroup variables
+ * Learn whether BitGroom quantization is on for a variable, and, if so,
+ * the NSD setting.
+ *
+ * @param ncid File ID.
+ * @param varid Variable ID. Must not be NC_GLOBAL.
+ * @param quantize_modep Pointer that gets a 0 if BitGroom is not in
+ * use for this var, and a 1 if it is. Ignored if NULL.
+ * @param nsdp Pointer that gets the NSD setting (from 1 to 15), if
+ * BitGroom is in use. Ignored if NULL.
+ *
+ * @return 0 for success, error code otherwise.
+ * @author Charlie Zender, Ed Hartnett
+*/
+int
+nc_inq_var_quantize(int ncid, int varid, int *quantize_modep, int *nsdp)
+{
+   NC* ncp;
+   int stat = NC_check_id(ncid,&ncp);
+
+   if(stat != NC_NOERR) return stat;
+   TRACE(nc_inq_var_quantize);
+   
+   /* Using NC_GLOBAL is illegal. */
+   if (varid == NC_GLOBAL) return NC_EGLOBAL;
+
+   return ncp->dispatch->inq_var_all(
+      ncid, varid,
+      NULL, /*name*/
+      NULL, /*xtypep*/
+      NULL, /*ndimsp*/
+      NULL, /*dimidsp*/
+      NULL, /*nattsp*/
+      NULL, /*shufflep*/
+      NULL, /*deflatep*/
+      NULL, /*deflatelevelp*/
+      NULL, /*fletcher32p*/
+      NULL, /*contiguousp*/
+      NULL, /*chunksizep*/
+      NULL, /*nofillp*/
+      NULL, /*fillvaluep*/
+      NULL, /*endianp*/
+      NULL, /* idp */
+      NULL, /* nparamsp */
+      NULL, /* params */
+      quantize_modep, 
+      nsdp);
+}
+
 /** \ingroup variables
 Find the endianness of a variable.
 
@@ -571,7 +632,11 @@ nc_inq_var_endian(int ncid, int varid, int *endianp)
       NULL, /*nofillp*/
       NULL, /*fillvaluep*/
       endianp, /*endianp*/
-      NULL, NULL, NULL);
+      NULL, /* idp */
+      NULL, /* nparamsp */
+      NULL, /* params */
+      NULL, /* quantize_modep */
+      NULL); /* nsdp */
 }
 
 /**
diff --git a/libhdf5/hdf5dispatch.c b/libhdf5/hdf5dispatch.c
index 60e00ecc62..53878b874d 100644
--- a/libhdf5/hdf5dispatch.c
+++ b/libhdf5/hdf5dispatch.c
@@ -105,6 +105,7 @@ static const NC_Dispatch HDF5_dispatcher = {
 
     NC4_hdf5_inq_var_filter_ids,
     NC4_hdf5_inq_var_filter_info,
+    NC4_def_var_quantize
 };
 
 const NC_Dispatch* HDF5_dispatch_table = NULL; /* moved here from ddispatch.c */
diff --git a/libhdf5/hdf5var.c b/libhdf5/hdf5var.c
index 45a218d448..22af7ab3b1 100644
--- a/libhdf5/hdf5var.c
+++ b/libhdf5/hdf5var.c
@@ -24,6 +24,14 @@
 /** Number of bytes in 64 KB. */
 #define SIXTY_FOUR_KB (65536)
 
+/** For quantization, the allowed value of number of significant
+ * digits for float. */
+#define MAX_FLOAT_NSD (14)
+
+/** For quantization, the allowed value of number of significant
+ * digits for double. */
+#define MAX_DOUBLE_NSD (14)
+
 #ifdef LOGGING
 /**
  * Report the chunksizes selected for a variable.
@@ -465,6 +473,8 @@ NC4_def_var(int ncid, const char *name, nc_type xtype, int ndims,
  * @param no_fill Pointer to no_fill setting.
  * @param fill_value Pointer to fill value.
  * @param endianness Pointer to endianness setting.
+ * @param quantize_mode Pointer to quantization mode.
+ * @param nsd Pointer to number of significant digits.
  *
  * @returns ::NC_NOERR for success
  * @returns ::NC_EBADID Bad ncid.
@@ -484,7 +494,8 @@ static int
 nc_def_var_extra(int ncid, int varid, int *shuffle, int *unused1,
                  int *unused2, int *fletcher32, int *storage,
                  const size_t *chunksizes, int *no_fill,
-                 const void *fill_value, int *endianness)
+                 const void *fill_value, int *endianness,
+		 int *quantize_mode, int *nsd)
 {
     NC_GRP_INFO_T *grp;
     NC_FILE_INFO_T *h5;
@@ -706,6 +717,60 @@ nc_def_var_extra(int ncid, int varid, int *shuffle, int *unused1,
 	var->endianness = *endianness;
     }
 
+    /* Remember quantization settings. They will be used when data are
+     * written. */
+    if (quantize_mode)
+    {
+	/* Only two valid mode settings. */
+	if (*quantize_mode != NC_NOQUANTIZE &&
+	    *quantize_mode != NC_QUANTIZE_BITGROOM)
+	    return NC_EINVAL;
+
+	if (*quantize_mode == NC_QUANTIZE_BITGROOM)
+	{
+	    /* Only float and double types can have quantization. */
+	    if (var->type_info->hdr.id != NC_FLOAT &&
+		var->type_info->hdr.id != NC_DOUBLE)
+		return NC_EINVAL;
+	    
+	    /* For bitgroom, number of significant digits is required. */
+	    if (!nsd)
+		return NC_EINVAL;
+
+	    /* NSD must be in range. */
+	    if (*nsd < 0)
+		return NC_EINVAL;
+	    if (var->type_info->hdr.id != NC_FLOAT && *nsd > MAX_FLOAT_NSD)
+		return NC_EINVAL;
+	    if (var->type_info->hdr.id != NC_DOUBLE && *nsd > MAX_DOUBLE_NSD)
+		return NC_EINVAL;
+
+	    var->nsd = *nsd;
+	}
+	
+	var->quantize_mode = *quantize_mode;
+
+	/* If nsd was zero, turn quantization off. */
+	if (*nsd == 0)
+	    var->quantize_mode = NC_NOQUANTIZE;
+	
+	/* If quantization is turned off, then set nsd to 0. */
+	if (*quantize_mode == NC_NOQUANTIZE)
+	    var->nsd = 0;
+    }
+
+    /* Setting nsd to 0 turns off quantization. */
+    if (nsd && !quantize_mode)
+    {
+	if (*nsd == 0)
+	{
+	    var->quantize_mode = NC_NOQUANTIZE;	    
+	    var->nsd = *nsd;
+	}
+	else
+	    return NC_EINVAL;
+    }
+
     return NC_NOERR;
 }
 
@@ -737,7 +802,8 @@ NC4_def_var_deflate(int ncid, int varid, int shuffle, int deflate,
     int stat = NC_NOERR;
     unsigned int level = (unsigned int)deflate_level;
     /* Set shuffle first */
-    if((stat = nc_def_var_extra(ncid, varid, &shuffle, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL))) goto done;
+    if((stat = nc_def_var_extra(ncid, varid, &shuffle, NULL, NULL, NULL,
+				NULL, NULL, NULL, NULL, NULL, NULL, NULL))) goto done;
     if(deflate) {
         if((stat = nc_def_var_filter(ncid, varid, H5Z_FILTER_DEFLATE,1,&level))) goto done;
     } /* else ignore */
@@ -746,6 +812,33 @@ NC4_def_var_deflate(int ncid, int varid, int shuffle, int deflate,
     return stat;
 }
 
+/**
+ * @internal Set quantization settings on a variable. This is
+ * called by nc_def_var_quantize().
+ *
+ * @param ncid File ID.
+ * @param varid Variable ID.
+ * @param quantize_mode Quantization mode.
+ * @param nsd Number of significant digits.
+ *
+ * @returns ::NC_NOERR No error.
+ * @returns ::NC_EBADID Bad ncid.
+ * @returns ::NC_ENOTVAR Invalid variable ID.
+ * @returns ::NC_ENOTNC4 Attempting netcdf-4 operation on file that is
+ * not netCDF-4/HDF5.
+ * @returns ::NC_ELATEDEF Too late to change settings for this variable.
+ * @returns ::NC_ENOTINDEFINE Not in define mode.
+ * @returns ::NC_EINVAL Invalid input
+ * @author Ed Hartnett, Dennis Heimbigner
+ */
+int
+NC4_def_var_quantize(int ncid, int varid, int quantize_mode, int nsd)
+{
+    return nc_def_var_extra(ncid, varid, NULL, NULL, NULL, NULL,
+			    NULL, NULL, NULL, NULL, NULL,
+			    &quantize_mode, &nsd);
+}
+
 #if 0
 /**
  * @internal Remove a filter from filter list for a variable
@@ -803,7 +896,7 @@ int
 NC4_def_var_fletcher32(int ncid, int varid, int fletcher32)
 {
     return nc_def_var_extra(ncid, varid, NULL, NULL, NULL, &fletcher32,
-                            NULL, NULL, NULL, NULL, NULL);
+                            NULL, NULL, NULL, NULL, NULL, NULL, NULL);
 }
 
 /**
@@ -832,7 +925,7 @@ int
 NC4_def_var_chunking(int ncid, int varid, int storage, const size_t *chunksizesp)
 {
     return nc_def_var_extra(ncid, varid, NULL, NULL, NULL, NULL,
-                            &storage, chunksizesp, NULL, NULL, NULL);
+                            &storage, chunksizesp, NULL, NULL, NULL, NULL, NULL);
 }
 
 /**
@@ -877,7 +970,7 @@ nc_def_var_chunking_ints(int ncid, int varid, int storage, int *chunksizesp)
         cs[i] = chunksizesp[i];
 
     retval = nc_def_var_extra(ncid, varid, NULL, NULL, NULL, NULL,
-                              &storage, cs, NULL, NULL, NULL);
+                              &storage, cs, NULL, NULL, NULL, NULL, NULL);
 
     if (var->ndims)
         free(cs);
@@ -911,7 +1004,7 @@ int
 NC4_def_var_fill(int ncid, int varid, int no_fill, const void *fill_value)
 {
     return nc_def_var_extra(ncid, varid, NULL, NULL, NULL, NULL, NULL,
-                            NULL, &no_fill, fill_value, NULL);
+                            NULL, &no_fill, fill_value, NULL, NULL, NULL);
 }
 
 /**
@@ -940,7 +1033,7 @@ int
 NC4_def_var_endian(int ncid, int varid, int endianness)
 {
     return nc_def_var_extra(ncid, varid, NULL, NULL, NULL, NULL, NULL,
-                            NULL, NULL, NULL, &endianness);
+                            NULL, NULL, NULL, &endianness, NULL, NULL);
 }
 
 /**
@@ -2053,6 +2146,8 @@ NC4_get_vars(int ncid, int varid, const size_t *startp, const size_t *countp,
  * @param nparamsp Pointer to memory to store filter parameter count.
  * @param params Pointer to vector of unsigned integers into which
  * to store filter parameters.
+ * @param quantize_modep Gets quantization mode.
+ * @param nsdp Gets number of significant digits, if quantization is in use.
  *
  * @returns ::NC_NOERR No error.
  * @returns ::NC_EBADID Bad ncid.
@@ -2067,7 +2162,8 @@ NC4_HDF5_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
                      int *shufflep, int *unused4, int *unused5,
                      int *fletcher32p, int *storagep, size_t *chunksizesp,
                      int *no_fill, void *fill_valuep, int *endiannessp,
-                     unsigned int *unused1, size_t *unused2, unsigned int *unused3)
+                     unsigned int *unused1, size_t *unused2, unsigned int *unused3,
+		     int *quantize_modep, int *nsdp)
 {
     NC_FILE_INFO_T *h5;
     NC_GRP_INFO_T *grp;
@@ -2088,7 +2184,49 @@ NC4_HDF5_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
     return NC4_inq_var_all(ncid, varid, name, xtypep, ndimsp, dimidsp, nattsp,
                            shufflep, unused4, unused5, fletcher32p,
                            storagep, chunksizesp, no_fill, fill_valuep,
-                           endiannessp, unused1, unused2, unused3);
+                           endiannessp, unused1, unused2, unused3,
+			   quantize_modep, nsdp);
+}
+
+/**
+ * @internal Get quantization information about a variable. Pass NULL
+ * for whatever you don't care about.
+ *
+ * @param ncid File ID.
+ * @param varid Variable ID.
+ *
+ * @returns ::NC_NOERR No error.
+ * @returns ::NC_EBADID Bad ncid.
+ * @returns ::NC_ENOTVAR Bad varid.
+ * @returns ::NC_ENOMEM Out of memory.
+ * @returns ::NC_EINVAL Invalid input.
+ * @author Ed Hartnett
+ */
+int
+NC4_HDF5_inq_var_quantize(int ncid, int varid, int *quantize_modep,
+			  int *nsdp)
+{
+    NC_FILE_INFO_T *h5;
+    NC_GRP_INFO_T *grp;
+    NC_VAR_INFO_T *var = NULL;
+    int retval;
+
+    LOG((2, "%s: ncid 0x%x varid %d", __func__, ncid, varid));
+
+    /* Find the file, group, and var info, and do lazy att read if
+     * needed. */
+    if ((retval = nc4_hdf5_find_grp_var_att(ncid, varid, NULL, 0, 0, NULL,
+                                            &h5, &grp, &var, NULL)))
+        return retval;
+    assert(grp && h5);
+
+    /* Now that lazy atts have been read, use the libsrc4 function to
+     * get the answers. */
+    return NC4_inq_var_all(ncid, varid, NULL, NULL, NULL, NULL, NULL,
+                           NULL, NULL, NULL, NULL,
+                           NULL, NULL, NULL, NULL,
+                           NULL, NULL, NULL, NULL,
+			   quantize_modep, nsdp);
 }
 
 /**
diff --git a/libhdf5/nc4hdf.c b/libhdf5/nc4hdf.c
index 7096023dc1..ebde9cbc6c 100644
--- a/libhdf5/nc4hdf.c
+++ b/libhdf5/nc4hdf.c
@@ -1016,9 +1016,17 @@ var_create_dataset(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var, nc_bool_t write_dimid
                 BAIL(retval);
     }
 
+    /* If quantization is in use, write an attribute indicating it, a
+     * single integer which is the number of significant digits. */
+    if ((retval = nc4_put_att(var->container, var->hdr.id, NC_QUANTIZE_ATT_NAME, NC_INT, 1,
+			      &var->nsd, NC_INT, 0)))
+	BAIL(retval);
+
     /* Write attributes for this var. */
     if ((retval = write_attlist(var->att, var->hdr.id, grp)))
         BAIL(retval);
+
+    /* The file is now up-to-date with all settings for this var. */
     var->attr_dirty = NC_FALSE;
 
 exit:
diff --git a/libnczarr/zdispatch.c b/libnczarr/zdispatch.c
index 5d1eef491c..bedc01ab08 100644
--- a/libnczarr/zdispatch.c
+++ b/libnczarr/zdispatch.c
@@ -105,6 +105,7 @@ static const NC_Dispatch NCZ_dispatcher = {
     NC4_get_var_chunk_cache,
     NCZ_inq_var_filter_ids,
     NCZ_inq_var_filter_info,
+    NC_NOTNC4_def_var_quantize,
 };
 
 const NC_Dispatch* NCZ_dispatch_table = NULL; /* moved here from ddispatch.c */
diff --git a/libnczarr/zdispatch.h b/libnczarr/zdispatch.h
index 346a0d3f7c..ab8c8c4cf2 100644
--- a/libnczarr/zdispatch.h
+++ b/libnczarr/zdispatch.h
@@ -82,7 +82,7 @@ EXTERNL int NCZ_put_att(int ncid, int varid, const char *name, nc_type file_type
 
 EXTERNL int NCZ_def_var(int ncid, const char *name, nc_type xtype, int ndims, const int *dimidsp, int *varidp);
 
-EXTERNL int NCZ_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep, int *ndimsp, int *dimidsp, int *nattsp, int *shufflep, int *deflatep, int *deflate_levelp, int *fletcher32p, int *contiguousp, size_t *chunksizesp, int *no_fill, void *fill_valuep, int *endiannessp, unsigned int* idp, size_t* nparamsp, unsigned int* params
+EXTERNL int NCZ_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep, int *ndimsp, int *dimidsp, int *nattsp, int *shufflep, int *deflatep, int *deflate_levelp, int *fletcher32p, int *contiguousp, size_t *chunksizesp, int *no_fill, void *fill_valuep, int *endiannessp, unsigned int* idp, size_t* nparamsp, unsigned int* params, int *quantize_modep, int *nsdp
 );
 
 EXTERNL int NCZ_inq_varid(int ncid, const char *name, int *varidp);
diff --git a/libnczarr/zvar.c b/libnczarr/zvar.c
index 7ba84f9683..83f2a777c5 100644
--- a/libnczarr/zvar.c
+++ b/libnczarr/zvar.c
@@ -1984,7 +1984,8 @@ NCZ_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
 		     int *shufflep, int *unused4, int *unused5,
 		     int *fletcher32p, int *storagep, size_t *chunksizesp,
 		     int *no_fill, void *fill_valuep, int *endiannessp,
-		     unsigned int *unused1, size_t *unused2, unsigned int *unused3)
+		unsigned int *unused1, size_t *unused2, unsigned int *unused3,
+		int *quantize_modep, int *nsdp)
 {
     NC_FILE_INFO_T *h5;
     NC_GRP_INFO_T *grp;
@@ -2007,7 +2008,7 @@ NCZ_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
     retval = NC4_inq_var_all(ncid, varid, name, xtypep, ndimsp, dimidsp, nattsp,
 			   shufflep, unused4, unused5, fletcher32p,
 			   storagep, chunksizesp, no_fill, fill_valuep,
-			   endiannessp, unused1, unused2, unused3);
+			     endiannessp, unused1, unused2, unused3, quantize_modep, nsdp);
 done:
     return ZUNTRACEX(retval,"xtype=%d natts=%d shuffle=%d fletcher32=%d no_fill=%d endianness=%d ndims=%d dimids=%s storage=%d chunksizes=%s",
 	   (xtypep?*xtypep:-1),
diff --git a/libnetcdf.settings.in b/libnetcdf.settings.in
index 0cc38514e1..d3cf633337 100644
--- a/libnetcdf.settings.in
+++ b/libnetcdf.settings.in
@@ -45,3 +45,5 @@ SZIP Write Support:     @HAS_SZLIB_WRITE@
 Parallel Filters:       @HAS_PAR_FILTERS@
 NCZarr Support:		@HAS_NCZARR@
 Multi-Filter Support:	@HAS_MULTIFILTERS@
+Quantization:		@HAS_QUANTIZE@
+
diff --git a/libsrc/nc3dispatch.c b/libsrc/nc3dispatch.c
index 8a6715d72a..f1238fcd0d 100644
--- a/libsrc/nc3dispatch.c
+++ b/libsrc/nc3dispatch.c
@@ -31,12 +31,13 @@
 
 
 static int NC3_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep, 
-               int *ndimsp, int *dimidsp, int *nattsp, 
-               int *shufflep, int *deflatep, int *deflate_levelp,
-               int *fletcher32p, int *contiguousp, size_t *chunksizesp, 
-               int *no_fill, void *fill_valuep, int *endiannessp, 
-	       unsigned int* idp, size_t* nparamsp, unsigned int* params
-               );
+			   int *ndimsp, int *dimidsp, int *nattsp, 
+			   int *shufflep, int *deflatep, int *deflate_levelp,
+			   int *fletcher32p, int *contiguousp, size_t *chunksizesp, 
+			   int *no_fill, void *fill_valuep, int *endiannessp, 
+			   unsigned int* idp, size_t* nparamsp, unsigned int* params,
+			   int *quantize_modep, int *nsdp
+    );
 
 static int NC3_var_par_access(int,int,int);
 
@@ -166,6 +167,8 @@ NC3_get_var_chunk_cache,
 
 NC_NOOP_inq_var_filter_ids,
 NC_NOOP_inq_var_filter_info,
+
+NC_NOTNC4_def_var_quantize
 };
 
 const NC_Dispatch* NC3_dispatch_table = NULL; /*!< NC3 Dispatch table, moved here from ddispatch.c */
@@ -185,12 +188,13 @@ NC3_finalize(void)
 
 static int
 NC3_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep, 
-               int *ndimsp, int *dimidsp, int *nattsp, 
-               int *shufflep, int *deflatep, int *deflate_levelp,
-               int *fletcher32p, int *contiguousp, size_t *chunksizesp, 
-               int *no_fill, void *fill_valuep, int *endiannessp, 
-	       unsigned int* idp, size_t* nparamsp, unsigned int* params
-	       )
+		int *ndimsp, int *dimidsp, int *nattsp, 
+		int *shufflep, int *deflatep, int *deflate_levelp,
+		int *fletcher32p, int *contiguousp, size_t *chunksizesp, 
+		int *no_fill, void *fill_valuep, int *endiannessp, 
+		unsigned int* idp, size_t* nparamsp, unsigned int* params,
+		int *quantize_modep, int *nsdp
+    )
 {
     int stat = NC3_inq_var(ncid,varid,name,xtypep,ndimsp,dimidsp,nattsp,no_fill,fill_valuep);
     if(stat) return stat;
@@ -202,6 +206,8 @@ NC3_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
     if(idp) return NC_ENOTNC4;
     if(nparamsp) return NC_ENOTNC4;
     if(params) return NC_ENOTNC4;
+    if(quantize_modep) return NC_ENOTNC4;
+    if(nsdp) return NC_ENOTNC4;
     return NC_NOERR;
 }
 
diff --git a/libsrc4/nc4var.c b/libsrc4/nc4var.c
index 559e84deab..4c938ff95f 100644
--- a/libsrc4/nc4var.c
+++ b/libsrc4/nc4var.c
@@ -136,6 +136,9 @@ nc_get_var_chunk_cache_ints(int ncid, int varid, int *sizep,
  * @param nparamsp Pointer to memory to store filter parameter count.
  * @param params Pointer to vector of unsigned integers into which
  * to store filter parameters.
+ * @param quantize_modep Pointer that gets the quantize mode.
+ * @param nsdp Pointer that gets the number of significant digits for
+ * quantization.
  *
  * @returns ::NC_NOERR No error.
  * @returns ::NC_EBADID Bad ncid.
@@ -150,7 +153,8 @@ NC4_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
                 int *shufflep, int *deflatep, int *deflate_levelp,
                 int *fletcher32p, int *storagep, size_t *chunksizesp,
                 int *no_fill, void *fill_valuep, int *endiannessp,
-                unsigned int *idp, size_t *nparamsp, unsigned int *params)
+                unsigned int *idp, size_t *nparamsp, unsigned int *params,
+		int *quantize_modep, int *nsdp)
 {
     NC_GRP_INFO_T *grp;
     NC_FILE_INFO_T *h5;
@@ -269,6 +273,12 @@ NC4_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
     if (endiannessp)
         *endiannessp = var->endianness;
 
+    /* Does the user want to know about quantization? */
+    if (quantize_modep)
+	*quantize_modep = var->quantize_mode;
+    if (nsdp)
+	*nsdp = var->nsd;
+
     return NC_NOERR;
 }
 
@@ -308,7 +318,7 @@ nc_inq_var_chunking_ints(int ncid, int varid, int *storagep, int *chunksizesp)
     /* Call the netcdf-4 version directly. */
     retval = NC4_inq_var_all(ncid, varid, NULL, NULL, NULL, NULL, NULL,
                              NULL, NULL, NULL, NULL, storagep, cs, NULL,
-                             NULL, NULL, NULL, NULL, NULL);
+                             NULL, NULL, NULL, NULL, NULL, NULL, NULL);
 
     /* Copy from size_t array. */
     if (!retval && chunksizesp && var->storage == NC_CHUNKED)
diff --git a/libsrcp/ncpdispatch.c b/libsrcp/ncpdispatch.c
index d2c344b499..294bfc1f0d 100644
--- a/libsrcp/ncpdispatch.c
+++ b/libsrcp/ncpdispatch.c
@@ -1463,6 +1463,8 @@ NC_NOTNC4_get_var_chunk_cache,
 
 NC_NOOP_inq_var_filter_ids,
 NC_NOOP_inq_var_filter_info,
+
+NC_NOTNC4_def_var_quantize,
 };
 
 const NC_Dispatch *NCP_dispatch_table = NULL; /* moved here from ddispatch.c */
diff --git a/nc_test4/CMakeLists.txt b/nc_test4/CMakeLists.txt
index c5c345005b..74dc93cf47 100644
--- a/nc_test4/CMakeLists.txt
+++ b/nc_test4/CMakeLists.txt
@@ -20,7 +20,7 @@ SET(NC4_TESTS tst_dims tst_dims2 tst_dims3 tst_files tst_files4
   tst_files6 tst_sync tst_h_strbug tst_h_refs tst_h_scalar tst_rename
   tst_rename2 tst_rename3 tst_h5_endians tst_atts_string_rewrite tst_put_vars_two_unlim_dim
   tst_hdf5_file_compat tst_fill_attr_vanish tst_rehash tst_types tst_bug324
-  tst_atts3 tst_put_vars tst_elatefill tst_udf tst_bug1442)
+  tst_atts3 tst_put_vars tst_elatefill tst_udf tst_bug1442 tst_quantize)
 
 # Note, renamegroup needs to be compiled before run_grp_rename
 
diff --git a/nc_test4/Makefile.am b/nc_test4/Makefile.am
index c356d50f08..3fb3bae8fc 100644
--- a/nc_test4/Makefile.am
+++ b/nc_test4/Makefile.am
@@ -35,7 +35,7 @@ tst_h_scalar tst_rename tst_rename2 tst_rename3 tst_h5_endians		\
 tst_atts_string_rewrite tst_hdf5_file_compat tst_fill_attr_vanish	\
 tst_rehash tst_filterparser tst_bug324 tst_types tst_atts3		\
 tst_put_vars tst_elatefill tst_udf tst_put_vars_two_unlim_dim		\
-tst_bug1442
+tst_bug1442 tst_quantize
 
 # Temporary I hoped, but hoped in vain.
 if !ISCYGWIN
diff --git a/nc_test4/tst_quantize.c b/nc_test4/tst_quantize.c
new file mode 100644
index 0000000000..fd9e4fd4ed
--- /dev/null
+++ b/nc_test4/tst_quantize.c
@@ -0,0 +1,68 @@
+/* This is part of the netCDF package.
+   Copyright 2021 University Corporation for Atmospheric Research/Unidata
+   See COPYRIGHT file for conditions of use.
+
+   Test quantization of netcdf-4 variables. Quantization is the
+   zeroing-out of bits in float or double data beyond a desired
+   precision.
+
+   Ed Hartnett, 8/19/21
+*/
+
+#include <nc_tests.h>
+#include "err_macros.h"
+#include "netcdf.h"
+
+#define FILE_NAME "tst_quantize.nc"
+#define NDIMS1 1
+#define DIM_NAME_1 "meters_along_canal"
+#define DIM_LEN_1 10
+#define VAR_NAME_1 "Amsterdam_houseboat_location"
+#define NSD_1 3
+
+int
+main(int argc, char **argv)
+{
+    printf("\n*** Testing netcdf-4 variable quantization functions.\n");
+    printf("**** testing simple quantization and error conditions...");
+    {
+	int ncid, dimid, varid;
+	int quantize_mode_in, nsd_in;
+
+	/* Create a netcdf classic file with one var. Attempt
+	 * quantization. It will not work. */
+	if (nc_create(FILE_NAME, NC_CLOBBER, &ncid)) ERR;
+	if (nc_def_dim(ncid, DIM_NAME_1, DIM_LEN_1, &dimid)) ERR;
+	if (nc_def_var(ncid, VAR_NAME_1, NC_FLOAT, NDIMS1, &dimid, &varid)) ERR;
+	if (nc_def_var_quantize(ncid, varid, NC_QUANTIZE_BITGROOM, NSD_1) != NC_ENOTNC4) ERR;
+	if (nc_inq_var_quantize(ncid, varid, &quantize_mode_in, &nsd_in) != NC_ENOTNC4) ERR;
+	if (nc_close(ncid)) ERR;
+
+	/* Create a netcdf-4 file with one var. Attempt
+	 * quantization. It will work, eventually... */
+	if (nc_create(FILE_NAME, NC_NETCDF4|NC_CLOBBER, &ncid)) ERR;
+	if (nc_def_dim(ncid, DIM_NAME_1, DIM_LEN_1, &dimid)) ERR;
+	if (nc_def_var(ncid, VAR_NAME_1, NC_FLOAT, NDIMS1, &dimid, &varid)) ERR;
+
+	/* Bad varid. */
+	if (nc_def_var_quantize(ncid, NC_GLOBAL, NC_QUANTIZE_BITGROOM, NSD_1) != NC_EGLOBAL) ERR;
+	if (nc_def_var_quantize(ncid, 1, NC_QUANTIZE_BITGROOM, NSD_1) != NC_ENOTVAR) ERR;
+
+	/* This will work. */
+	if (nc_def_var_quantize(ncid, varid, NC_QUANTIZE_BITGROOM, NSD_1)) ERR;
+	if (nc_inq_var_quantize(ncid, varid, &quantize_mode_in, &nsd_in)) ERR;
+	if (quantize_mode_in != NC_QUANTIZE_BITGROOM) ERR;
+	if (nsd_in != NSD_1) ERR;
+	if (nc_close(ncid)) ERR;
+
+	/* Open the file and check. */
+	if (nc_open(FILE_NAME, NC_WRITE, &ncid)) ERR;
+	if (nc_inq_var_quantize(ncid, 0, &quantize_mode_in, &nsd_in)) ERR;
+	printf("quantize_mode_in %d nsd_in %d\n", quantize_mode_in, nsd_in);
+	/* if (quantize_mode_in != NC_QUANTIZE_BITGROOM) ERR; */
+	/* if (nsd_in != NSD_1) ERR; */
+	if (nc_close(ncid)) ERR;
+    }
+    SUMMARIZE_ERR;
+    FINAL_RESULTS;
+}
diff --git a/nc_test4/tst_udf.c b/nc_test4/tst_udf.c
index b4e390e84d..522fa4c816 100644
--- a/nc_test4/tst_udf.c
+++ b/nc_test4/tst_udf.c
@@ -156,6 +156,9 @@ static NC_Dispatch tst_dispatcher = {
     NC_NOOP_inq_var_filter_ids,
     NC_NOOP_inq_var_filter_info,
 #endif
+#if NC_DISPATCH_VERSION >= 4
+    NC_NOTNC4_def_var_quantize,
+#endif
 };
 
 /* This is the dispatch object that holds pointers to all the