diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index e0c8b1a8..6e310cf5 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -5,6 +5,9 @@ on:
   pull_request:
   workflow_dispatch:
 
+env:
+  FORM_IGNORE_DEPRECATION: 1
+
 jobs:
   # Generate the tarball distribution, e.g., "form-v4.2.1.tar.gz" for v4.2.1.
   # The tarball will be tested in the following "build-bin" job.
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index dce6465e..15a9455c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -5,6 +5,9 @@ on:
   pull_request:
   workflow_dispatch:
 
+env:
+  FORM_IGNORE_DEPRECATION: 1
+
 jobs:
   # Simple tests on Linux; except the ParFORM case, they probably pass unless
   # the committer has forgotten running "make check".
diff --git a/sources/checkpoint.c b/sources/checkpoint.c
index 9bf64e6f..5df5f291 100644
--- a/sources/checkpoint.c
+++ b/sources/checkpoint.c
@@ -840,6 +840,7 @@ static void print_M()
 	MesPrint("%d", AM.ggShortStatsMax);
 	MesPrint("--MARK 11");
 	MesPrint("%d", AM.FromStdin);
+	MesPrint("%d", AM.IgnoreDeprecation);
 	MesPrint("%%%% END M_const");
 /*	fflush(0); */
 }
@@ -1503,6 +1504,7 @@ int DoRecovery(int *moduletype)
 	R_COPY_S(AM.Path,UBYTE *);
 
 	R_SET(AM.FromStdin, BOOL);
+	R_SET(AM.IgnoreDeprecation, BOOL);
 
 #ifdef PRINTDEBUG
 	print_M();
@@ -2574,6 +2576,7 @@ static int DoSnapshot(int moduletype)
 	S_WRITE_S(AM.Path);
 
 	S_WRITE_B(&AM.FromStdin,sizeof(BOOL));
+	S_WRITE_B(&AM.IgnoreDeprecation,sizeof(BOOL));
 
 	/*#] AM :*/ 
 	/*#[ AC :*/
diff --git a/sources/compcomm.c b/sources/compcomm.c
index d76973ad..53a0f5a3 100644
--- a/sources/compcomm.c
+++ b/sources/compcomm.c
@@ -608,6 +608,7 @@ int CoOff(UBYTE *s)
 			AR.gzipCompress = 0;
 		}
 		else if ( StrICont(t,(UBYTE *)"checkpoint") == 0 ) {
+			PrintDeprecation("the checkpoint mechanism", "issues/626");
 			AC.CheckpointInterval = 0;
 			if ( AC.CheckpointRunBefore ) { free(AC.CheckpointRunBefore); AC.CheckpointRunBefore = NULL; }
 			if ( AC.CheckpointRunAfter ) { free(AC.CheckpointRunAfter); AC.CheckpointRunAfter = NULL; }
@@ -706,6 +707,7 @@ int CoOn(UBYTE *s)
 			}
 		}
 		else if ( StrICont(t,(UBYTE *)"checkpoint") == 0 ) {
+			PrintDeprecation("the checkpoint mechanism", "issues/626");
 			AC.CheckpointInterval = 0;
 			if ( AC.CheckpointRunBefore ) { free(AC.CheckpointRunBefore); AC.CheckpointRunBefore = NULL; }
 			if ( AC.CheckpointRunAfter ) { free(AC.CheckpointRunAfter); AC.CheckpointRunAfter = NULL; }
diff --git a/sources/declare.h b/sources/declare.h
index 15c26b42..6f3410df 100644
--- a/sources/declare.h
+++ b/sources/declare.h
@@ -672,6 +672,7 @@ extern WORD   Processor(VOID);
 extern WORD   Product(UWORD *,WORD *,WORD);
 extern VOID   PrtLong(UWORD *,WORD,UBYTE *);
 extern VOID   PrtTerms(VOID);
+extern void   PrintDeprecation(const char *,const char *);
 extern VOID   PrintRunningTime(VOID);
 extern LONG   GetRunningTime(VOID);
 extern WORD   PutBracket(PHEAD WORD *);
diff --git a/sources/startup.c b/sources/startup.c
index 58e6ade4..d4baf1a9 100644
--- a/sources/startup.c
+++ b/sources/startup.c
@@ -194,6 +194,18 @@ static void PrintHeader(int with_full_info)
 			AC.LineLength = oldLineLength;
 		}
 	}
+#ifdef WINDOWS
+	PrintDeprecation("the native Windows version", "issues/623");
+#endif
+#ifdef ILP32
+	PrintDeprecation("the 32-bit version", "issues/624");
+#endif
+#ifdef WITHMPI
+	PrintDeprecation("the MPI version (ParFORM)", "issues/625");
+#endif
+	if ( AC.CheckpointFlag ) {
+		PrintDeprecation("the checkpoint mechanism", "issues/626");
+	}
 }
 
 /*
@@ -261,9 +273,17 @@ int DoTail(int argc, UBYTE **argv)
 							AM.FileOnlyFlag = 1; AM.LogType = 1; break;
 				case 'h': /* For old systems: wait for key before exit */
 							AM.HoldFlag = 1; break;
+				case 'i':
+							if ( StrCmp(s, (UBYTE *)"ignore-deprecation") == 0 ) {
+								AM.IgnoreDeprecation = 1;
+								break;
+							}
 #ifdef WITHINTERACTION
-				case 'i': /* Interactive session (not used yet) */
-							AM.Interact = 1; break;
+							/* Interactive session (not used yet) */
+							AM.Interact = 1;
+							break;
+#else
+							goto IllegalOption;
 #endif
 				case 'I': /* Next arg is dir for inc/prc/sub files */
 							TAKEPATH(AM.IncDir)  break;
@@ -426,6 +446,7 @@ printversion:;
 							}
 						}
 						else {
+IllegalOption:
 #ifdef WITHMPI
 							if ( PF.me == MASTER )
 #endif
@@ -1890,6 +1911,36 @@ VOID Terminate(int errorcode)
 
 /*
  		#] Terminate : 
+ 		#[ PrintDeprecation :
+*/
+
+/**
+ * Prints a deprecation warning for a given feature.
+ *
+ * @param feature  The name of the deprecated feature.
+ * @param issue    The associated issue, e.g., "issues/700".
+ */
+void PrintDeprecation(const char *feature, const char *issue) {
+#ifdef WITHMPI
+	if ( PF.me != MASTER ) return;
+#endif
+	if ( AM.IgnoreDeprecation ) return;
+
+	UBYTE *e = (UBYTE *)getenv("FORM_IGNORE_DEPRECATION");
+	if ( e && e[0] && StrCmp(e, (UBYTE *)"0") && StrICmp(e, (UBYTE *)"false") && StrICmp(e, (UBYTE *)"no") ) return;
+
+	MesPrint("DeprecationWarning: We are considering deprecating %s.", feature);
+	MesPrint("If you want this support to continue, leave a comment at:");
+	MesPrint("");
+	MesPrint("    https://github.com/vermaseren/form/%s", issue);
+	MesPrint("");
+	MesPrint("Otherwise, it will be discontinued in the future.");
+	MesPrint("To suppress this warning, use the -ignore-deprecation command line option or");
+	MesPrint("set the environment variable FORM_IGNORE_DEPRECATION=1.");
+}
+
+/*
+ 		#] PrintDeprecation : 
  		#[ PrintRunningTime :
 */
 
diff --git a/sources/structs.h b/sources/structs.h
index 9daaa0cb..4c2ffff5 100644
--- a/sources/structs.h
+++ b/sources/structs.h
@@ -1600,11 +1600,12 @@ struct M_const {
     WORD    numpi;
     WORD    BracketFactors[8];
     BOOL    FromStdin;             /* read the input from STDIN */
+    BOOL    IgnoreDeprecation;     /* ignore deprecation warning */
 #ifdef WITHFLOAT
 #ifdef WITHPTHREADS
 	PADPOSITION(17,30,62,84,(sizeof(pthread_rwlock_t)+sizeof(pthread_mutex_t)*2)+1);
 #else
-	PADPOSITION(17,28,62,84,1);
+	PADPOSITION(17,28,62,84,2);
 #endif
 #else
 #ifdef WITHPTHREADS