diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 33b3e800374e3..58c8a7d82bfb5 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -1,4 +1,5 @@
 use std::collections::BTreeMap;
+use std::convert::TryFrom;
 use std::ffi::OsStr;
 use std::fmt;
 use std::path::PathBuf;
@@ -24,6 +25,33 @@ use crate::opts;
 use crate::passes::{self, Condition, DefaultPassOption};
 use crate::theme;
 
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub enum OutputFormat {
+    Json,
+    Html,
+}
+
+impl OutputFormat {
+    pub fn is_json(&self) -> bool {
+        match self {
+            OutputFormat::Json => true,
+            _ => false,
+        }
+    }
+}
+
+impl TryFrom<&str> for OutputFormat {
+    type Error = String;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        match value {
+            "json" => Ok(OutputFormat::Json),
+            "html" => Ok(OutputFormat::Html),
+            _ => Err(format!("unknown output format `{}`", value)),
+        }
+    }
+}
+
 /// Configuration options for rustdoc.
 #[derive(Clone)]
 pub struct Options {
@@ -115,6 +143,8 @@ pub struct Options {
     pub crate_version: Option<String>,
     /// Collected options specific to outputting final pages.
     pub render_options: RenderOptions,
+    /// Output format rendering (used only for "show-coverage" option for the moment)
+    pub output_format: Option<OutputFormat>,
 }
 
 impl fmt::Debug for Options {
@@ -425,14 +455,6 @@ impl Options {
             }
         }
 
-        match matches.opt_str("w").as_ref().map(|s| &**s) {
-            Some("html") | None => {}
-            Some(s) => {
-                diag.struct_err(&format!("unknown output format: {}", s)).emit();
-                return Err(1);
-            }
-        }
-
         let index_page = matches.opt_str("index-page").map(|s| PathBuf::from(&s));
         if let Some(ref index_page) = index_page {
             if !index_page.is_file() {
@@ -469,6 +491,29 @@ impl Options {
             }
         };
 
+        let output_format = match matches.opt_str("output-format") {
+            Some(s) => match OutputFormat::try_from(s.as_str()) {
+                Ok(o) => {
+                    if o.is_json() && !show_coverage {
+                        diag.struct_err("json output format isn't supported for doc generation")
+                            .emit();
+                        return Err(1);
+                    } else if !o.is_json() && show_coverage {
+                        diag.struct_err(
+                            "html output format isn't supported for the --show-coverage option",
+                        )
+                        .emit();
+                        return Err(1);
+                    }
+                    Some(o)
+                }
+                Err(e) => {
+                    diag.struct_err(&e).emit();
+                    return Err(1);
+                }
+            },
+            None => None,
+        };
         let crate_name = matches.opt_str("crate-name");
         let proc_macro_crate = crate_types.contains(&CrateType::ProcMacro);
         let playground_url = matches.opt_str("playground-url");
@@ -553,6 +598,7 @@ impl Options {
                 generate_search_filter,
                 generate_redirect_pages,
             },
+            output_format,
         })
     }
 
@@ -568,6 +614,9 @@ fn check_deprecated_options(matches: &getopts::Matches, diag: &rustc_errors::Han
 
     for flag in deprecated_flags.iter() {
         if matches.opt_present(flag) {
+            if *flag == "output-format" && matches.opt_present("show-coverage") {
+                continue;
+            }
             let mut err =
                 diag.struct_warn(&format!("the '{}' flag is considered deprecated", flag));
             err.warn(
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 8bc34e949f175..b9ae3d53afc04 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -228,6 +228,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         mut manual_passes,
         display_warnings,
         render_options,
+        output_format,
         ..
     } = options;
 
@@ -385,6 +386,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
 
                 let mut renderinfo = RenderInfo::default();
                 renderinfo.access_levels = access_levels;
+                renderinfo.output_format = output_format;
 
                 let mut ctxt = DocContext {
                     tcx,
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index d3015b403fc4c..2d1e3c29055cf 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -60,7 +60,7 @@ use serde::ser::SerializeSeq;
 use serde::{Serialize, Serializer};
 
 use crate::clean::{self, AttributesExt, Deprecation, GetDefId, SelfTy};
-use crate::config::RenderOptions;
+use crate::config::{OutputFormat, RenderOptions};
 use crate::docfs::{DocFS, ErrorStorage, PathError};
 use crate::doctree;
 use crate::html::escape::Escape;
@@ -270,6 +270,7 @@ pub struct RenderInfo {
     pub deref_trait_did: Option<DefId>,
     pub deref_mut_trait_did: Option<DefId>,
     pub owned_box_did: Option<DefId>,
+    pub output_format: Option<OutputFormat>,
 }
 
 // Helper structs for rendering items/sidebars and carrying along contextual
diff --git a/src/librustdoc/html/render/cache.rs b/src/librustdoc/html/render/cache.rs
index a0a35e4ce4b85..4198369eca8f5 100644
--- a/src/librustdoc/html/render/cache.rs
+++ b/src/librustdoc/html/render/cache.rs
@@ -139,6 +139,7 @@ impl Cache {
             deref_trait_did,
             deref_mut_trait_did,
             owned_box_did,
+            ..
         } = renderinfo;
 
         let external_paths =
diff --git a/src/librustdoc/passes/calculate_doc_coverage.rs b/src/librustdoc/passes/calculate_doc_coverage.rs
index d4a7f3313a49b..f48224512ba4f 100644
--- a/src/librustdoc/passes/calculate_doc_coverage.rs
+++ b/src/librustdoc/passes/calculate_doc_coverage.rs
@@ -1,4 +1,5 @@
 use crate::clean;
+use crate::config::OutputFormat;
 use crate::core::DocContext;
 use crate::fold::{self, DocFolder};
 use crate::passes::Pass;
@@ -6,6 +7,8 @@ use crate::passes::Pass;
 use rustc_ast::attr;
 use rustc_span::symbol::sym;
 use rustc_span::FileName;
+use serde::Serialize;
+use serde_json;
 
 use std::collections::BTreeMap;
 use std::ops;
@@ -16,16 +19,16 @@ pub const CALCULATE_DOC_COVERAGE: Pass = Pass {
     description: "counts the number of items with and without documentation",
 };
 
-fn calculate_doc_coverage(krate: clean::Crate, _: &DocContext<'_>) -> clean::Crate {
-    let mut calc = CoverageCalculator::default();
+fn calculate_doc_coverage(krate: clean::Crate, ctx: &DocContext<'_>) -> clean::Crate {
+    let mut calc = CoverageCalculator::new();
     let krate = calc.fold_crate(krate);
 
-    calc.print_results();
+    calc.print_results(ctx.renderinfo.borrow().output_format);
 
     krate
 }
 
-#[derive(Default, Copy, Clone)]
+#[derive(Default, Copy, Clone, Serialize)]
 struct ItemCount {
     total: u64,
     with_docs: u64,
@@ -64,13 +67,41 @@ impl ops::AddAssign for ItemCount {
     }
 }
 
-#[derive(Default)]
 struct CoverageCalculator {
     items: BTreeMap<FileName, ItemCount>,
 }
 
+fn limit_filename_len(filename: String) -> String {
+    let nb_chars = filename.chars().count();
+    if nb_chars > 35 {
+        "...".to_string()
+            + &filename[filename.char_indices().nth(nb_chars - 32).map(|x| x.0).unwrap_or(0)..]
+    } else {
+        filename
+    }
+}
+
 impl CoverageCalculator {
-    fn print_results(&self) {
+    fn new() -> CoverageCalculator {
+        CoverageCalculator { items: Default::default() }
+    }
+
+    fn to_json(&self) -> String {
+        serde_json::to_string(
+            &self
+                .items
+                .iter()
+                .map(|(k, v)| (k.to_string(), v))
+                .collect::<BTreeMap<String, &ItemCount>>(),
+        )
+        .expect("failed to convert JSON data to string")
+    }
+
+    fn print_results(&self, output_format: Option<OutputFormat>) {
+        if output_format.map(|o| o.is_json()).unwrap_or_else(|| false) {
+            println!("{}", self.to_json());
+            return;
+        }
         let mut total = ItemCount::default();
 
         fn print_table_line() {
@@ -93,15 +124,7 @@ impl CoverageCalculator {
 
         for (file, &count) in &self.items {
             if let Some(percentage) = count.percentage() {
-                let mut name = file.to_string();
-                // if a filename is too long, shorten it so we don't blow out the table
-                // FIXME(misdreavus): this needs to count graphemes, and probably also track
-                // double-wide characters...
-                if name.len() > 35 {
-                    name = "...".to_string() + &name[name.len() - 32..];
-                }
-
-                print_table_record(&name, count, percentage);
+                print_table_record(&limit_filename_len(file.to_string()), count, percentage);
 
                 total += count;
             }
diff --git a/src/test/rustdoc-ui/coverage/html.rs b/src/test/rustdoc-ui/coverage/html.rs
new file mode 100644
index 0000000000000..181cb4c5061a7
--- /dev/null
+++ b/src/test/rustdoc-ui/coverage/html.rs
@@ -0,0 +1,4 @@
+// compile-flags:-Z unstable-options --output-format html --show-coverage
+
+/// Foo
+pub struct Xo;
diff --git a/src/test/rustdoc-ui/coverage/html.stderr b/src/test/rustdoc-ui/coverage/html.stderr
new file mode 100644
index 0000000000000..adca375d4bce5
--- /dev/null
+++ b/src/test/rustdoc-ui/coverage/html.stderr
@@ -0,0 +1,2 @@
+error: html output format isn't supported for the --show-coverage option
+
diff --git a/src/test/rustdoc-ui/coverage/json.rs b/src/test/rustdoc-ui/coverage/json.rs
new file mode 100644
index 0000000000000..b1220b32e9194
--- /dev/null
+++ b/src/test/rustdoc-ui/coverage/json.rs
@@ -0,0 +1,27 @@
+// build-pass
+// compile-flags:-Z unstable-options --output-format json --show-coverage
+
+pub mod foo {
+    /// Hello!
+    pub struct Foo;
+    /// Bar
+    pub enum Bar { A }
+}
+
+/// X
+pub struct X;
+
+/// Bar
+pub mod bar {
+    /// bar
+    pub struct Bar;
+    /// X
+    pub enum X { Y }
+}
+
+/// yolo
+pub enum Yolo { X }
+
+pub struct Xo<T: Clone> {
+    x: T,
+}
diff --git a/src/test/rustdoc-ui/coverage/json.stdout b/src/test/rustdoc-ui/coverage/json.stdout
new file mode 100644
index 0000000000000..63b22a7d94b00
--- /dev/null
+++ b/src/test/rustdoc-ui/coverage/json.stdout
@@ -0,0 +1 @@
+{"$DIR/json.rs":{"total":13,"with_docs":7}}
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 424bac88c8531..680c32c92af4b 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -3204,7 +3204,9 @@ impl<'test> TestCx<'test> {
         let json = cflags.contains("--error-format json")
             || cflags.contains("--error-format pretty-json")
             || cflags.contains("--error-format=json")
-            || cflags.contains("--error-format=pretty-json");
+            || cflags.contains("--error-format=pretty-json")
+            || cflags.contains("--output-format json")
+            || cflags.contains("--output-format=json");
 
         let mut normalized = output.to_string();