diff --git a/include/jemalloc/internal/emitter.h b/include/jemalloc/internal/emitter.h
index 542bc79c..009bf9ac 100644
--- a/include/jemalloc/internal/emitter.h
+++ b/include/jemalloc/internal/emitter.h
@@ -6,6 +6,7 @@
 typedef enum emitter_output_e emitter_output_t;
 enum emitter_output_e {
 	emitter_output_json,
+	emitter_output_json_compact,
 	emitter_output_table
 };
 
@@ -75,6 +76,12 @@ struct emitter_s {
 	bool emitted_key;
 };
 
+static inline bool
+emitter_outputs_json(emitter_t *emitter) {
+	return emitter->output == emitter_output_json ||
+	    emitter->output == emitter_output_json_compact;
+}
+
 /* Internal convenience function.  Write to the emitter the given string. */
 JEMALLOC_FORMAT_PRINTF(2, 3)
 static inline void
@@ -135,7 +142,7 @@ emitter_print_value(emitter_t *emitter, emitter_justify_t justify, int width,
 
 	switch (value_type) {
 	case emitter_type_bool:
-		emitter_printf(emitter, 
+		emitter_printf(emitter,
 		    emitter_gen_fmt(fmt, FMT_SIZE, "%s", justify, width),
 		    *(const bool *)value ?  "true" : "false");
 		break;
@@ -159,7 +166,7 @@ emitter_print_value(emitter_t *emitter, emitter_justify_t justify, int width,
 		 * anywhere near the fmt size.
 		 */
 		assert(str_written < BUF_SIZE);
-		emitter_printf(emitter, 
+		emitter_printf(emitter,
 		    emitter_gen_fmt(fmt, FMT_SIZE, "%s", justify, width), buf);
 		break;
 	case emitter_type_uint32:
@@ -196,6 +203,7 @@ static inline void
 emitter_indent(emitter_t *emitter) {
 	int amount = emitter->nesting_depth;
 	const char *indent_str;
+	assert(emitter->output != emitter_output_json_compact);
 	if (emitter->output == emitter_output_json) {
 		indent_str = "\t";
 	} else {
@@ -209,12 +217,18 @@ emitter_indent(emitter_t *emitter) {
 
 static inline void
 emitter_json_key_prefix(emitter_t *emitter) {
+	assert(emitter_outputs_json(emitter));
 	if (emitter->emitted_key) {
 		emitter->emitted_key = false;
 		return;
 	}
-	emitter_printf(emitter, "%s\n", emitter->item_at_depth ? "," : "");
-	emitter_indent(emitter);
+	if (emitter->item_at_depth) {
+		emitter_printf(emitter, ",");
+	}
+	if (emitter->output != emitter_output_json_compact) {
+		emitter_printf(emitter, "\n");
+		emitter_indent(emitter);
+	}
 }
 
 /******************************************************************************/
@@ -227,22 +241,23 @@ emitter_init(emitter_t *emitter, emitter_output_t emitter_output,
 	emitter->write_cb = write_cb;
 	emitter->cbopaque = cbopaque;
 	emitter->item_at_depth = false;
-	emitter->emitted_key = false; 
+	emitter->emitted_key = false;
 	emitter->nesting_depth = 0;
 }
 
 /******************************************************************************/
 /* JSON public API. */
 
-/* 
+/*
  * Emits a key (e.g. as appears in an object). The next json entity emitted will
  * be the corresponding value.
  */
 static inline void
 emitter_json_key(emitter_t *emitter, const char *json_key) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		emitter_json_key_prefix(emitter);
-		emitter_printf(emitter, "\"%s\": ", json_key);
+		emitter_printf(emitter, "\"%s\":%s", json_key,
+		    emitter->output == emitter_output_json_compact ? "" : " ");
 		emitter->emitted_key = true;
 	}
 }
@@ -250,7 +265,7 @@ emitter_json_key(emitter_t *emitter, const char *json_key) {
 static inline void
 emitter_json_value(emitter_t *emitter, emitter_type_t value_type,
     const void *value) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		emitter_json_key_prefix(emitter);
 		emitter_print_value(emitter, emitter_justify_none, -1,
 		    value_type, value);
@@ -268,7 +283,7 @@ emitter_json_kv(emitter_t *emitter, const char *json_key,
 
 static inline void
 emitter_json_array_begin(emitter_t *emitter) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		emitter_json_key_prefix(emitter);
 		emitter_printf(emitter, "[");
 		emitter_nest_inc(emitter);
@@ -284,18 +299,20 @@ emitter_json_array_kv_begin(emitter_t *emitter, const char *json_key) {
 
 static inline void
 emitter_json_array_end(emitter_t *emitter) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		assert(emitter->nesting_depth > 0);
 		emitter_nest_dec(emitter);
-		emitter_printf(emitter, "\n");
-		emitter_indent(emitter);
+		if (emitter->output != emitter_output_json_compact) {
+			emitter_printf(emitter, "\n");
+			emitter_indent(emitter);
+		}
 		emitter_printf(emitter, "]");
 	}
 }
 
 static inline void
 emitter_json_object_begin(emitter_t *emitter) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		emitter_json_key_prefix(emitter);
 		emitter_printf(emitter, "{");
 		emitter_nest_inc(emitter);
@@ -311,11 +328,13 @@ emitter_json_object_kv_begin(emitter_t *emitter, const char *json_key) {
 
 static inline void
 emitter_json_object_end(emitter_t *emitter) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		assert(emitter->nesting_depth > 0);
 		emitter_nest_dec(emitter);
-		emitter_printf(emitter, "\n");
-		emitter_indent(emitter);
+		if (emitter->output != emitter_output_json_compact) {
+			emitter_printf(emitter, "\n");
+			emitter_indent(emitter);
+		}
 		emitter_printf(emitter, "}");
 	}
 }
@@ -420,7 +439,7 @@ emitter_kv_note(emitter_t *emitter, const char *json_key, const char *table_key,
     emitter_type_t value_type, const void *value,
     const char *table_note_key, emitter_type_t table_note_value_type,
     const void *table_note_value) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		emitter_json_key(emitter, json_key);
 		emitter_json_value(emitter, value_type, value);
 	} else {
@@ -440,7 +459,7 @@ emitter_kv(emitter_t *emitter, const char *json_key, const char *table_key,
 static inline void
 emitter_dict_begin(emitter_t *emitter, const char *json_key,
     const char *table_header) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		emitter_json_key(emitter, json_key);
 		emitter_json_object_begin(emitter);
 	} else {
@@ -450,7 +469,7 @@ emitter_dict_begin(emitter_t *emitter, const char *json_key,
 
 static inline void
 emitter_dict_end(emitter_t *emitter) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		emitter_json_object_end(emitter);
 	} else {
 		emitter_table_dict_end(emitter);
@@ -459,7 +478,7 @@ emitter_dict_end(emitter_t *emitter) {
 
 static inline void
 emitter_begin(emitter_t *emitter) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		assert(emitter->nesting_depth == 0);
 		emitter_printf(emitter, "{");
 		emitter_nest_inc(emitter);
@@ -476,10 +495,11 @@ emitter_begin(emitter_t *emitter) {
 
 static inline void
 emitter_end(emitter_t *emitter) {
-	if (emitter->output == emitter_output_json) {
+	if (emitter_outputs_json(emitter)) {
 		assert(emitter->nesting_depth == 1);
 		emitter_nest_dec(emitter);
-		emitter_printf(emitter, "\n}\n");
+		emitter_printf(emitter, "%s", emitter->output ==
+		    emitter_output_json_compact ? "}" : "\n}\n");
 	}
 }
 
diff --git a/test/unit/emitter.c b/test/unit/emitter.c
index b4a693f4..712c9e10 100644
--- a/test/unit/emitter.c
+++ b/test/unit/emitter.c
@@ -66,7 +66,9 @@ forwarding_cb(void *buf_descriptor_v, const char *str) {
 
 static void
 assert_emit_output(void (*emit_fn)(emitter_t *),
-    const char *expected_json_output, const char *expected_table_output) {
+    const char *expected_json_output,
+    const char *expected_json_compact_output,
+    const char *expected_table_output) {
 	emitter_t emitter;
 	char buf[MALLOC_PRINTF_BUFSIZE];
 	buf_descriptor_t buf_descriptor;
@@ -84,6 +86,16 @@ assert_emit_output(void (*emit_fn)(emitter_t *),
 	buf_descriptor.len = MALLOC_PRINTF_BUFSIZE;
 	buf_descriptor.mid_quote = false;
 
+	emitter_init(&emitter, emitter_output_json_compact, &forwarding_cb,
+	    &buf_descriptor);
+	(*emit_fn)(&emitter);
+	assert_str_eq(expected_json_compact_output, buf,
+	    "compact json output failure");
+
+	buf_descriptor.buf = buf;
+	buf_descriptor.len = MALLOC_PRINTF_BUFSIZE;
+	buf_descriptor.mid_quote = false;
+
 	emitter_init(&emitter, emitter_output_table, &forwarding_cb,
 	    &buf_descriptor);
 	(*emit_fn)(&emitter);
@@ -108,6 +120,7 @@ emit_dict(emitter_t *emitter) {
 	emitter_dict_end(emitter);
 	emitter_end(emitter);
 }
+
 static const char *dict_json =
 "{\n"
 "\t\"foo\": {\n"
@@ -117,6 +130,15 @@ static const char *dict_json =
 "\t\t\"jkl\": \"a string\"\n"
 "\t}\n"
 "}\n";
+static const char *dict_json_compact =
+"{"
+	"\"foo\":{"
+		"\"abc\":false,"
+		"\"def\":true,"
+		"\"ghi\":123,"
+		"\"jkl\":\"a string\""
+	"}"
+"}";
 static const char *dict_table =
 "This is the foo table:\n"
 "  ABC: false\n"
@@ -124,11 +146,6 @@ static const char *dict_table =
 "  GHI: 123 (note_key1: \"a string\")\n"
 "  JKL: \"a string\" (note_key2: false)\n";
 
-TEST_BEGIN(test_dict) {
-	assert_emit_output(&emit_dict, dict_json, dict_table);
-}
-TEST_END
-
 static void
 emit_table_printf(emitter_t *emitter) {
 	emitter_begin(emitter);
@@ -141,17 +158,11 @@ emit_table_printf(emitter_t *emitter) {
 static const char *table_printf_json =
 "{\n"
 "}\n";
-
+static const char *table_printf_json_compact = "{}";
 static const char *table_printf_table =
 "Table note 1\n"
 "Table note 2 with format string\n";
 
-TEST_BEGIN(test_table_printf) {
-	assert_emit_output(&emit_table_printf, table_printf_json,
-	    table_printf_table);
-}
-TEST_END
-
 static void emit_nested_dict(emitter_t *emitter) {
 	int val = 123;
 	emitter_begin(emitter);
@@ -169,7 +180,7 @@ static void emit_nested_dict(emitter_t *emitter) {
 	emitter_end(emitter);
 }
 
-static const char *nested_object_json =
+static const char *nested_dict_json =
 "{\n"
 "\t\"json1\": {\n"
 "\t\t\"json2\": {\n"
@@ -182,8 +193,20 @@ static const char *nested_object_json =
 "\t\t\"primitive\": 123\n"
 "\t}\n"
 "}\n";
-
-static const char *nested_object_table =
+static const char *nested_dict_json_compact =
+"{"
+	"\"json1\":{"
+		"\"json2\":{"
+			"\"primitive\":123"
+		"},"
+		"\"json3\":{"
+		"}"
+	"},"
+	"\"json4\":{"
+		"\"primitive\":123"
+	"}"
+"}";
+static const char *nested_dict_table =
 "Dict 1\n"
 "  Dict 2\n"
 "    A primitive: 123\n"
@@ -191,12 +214,6 @@ static const char *nested_object_table =
 "Dict 4\n"
 "  Another primitive: 123\n";
 
-TEST_BEGIN(test_nested_dict) {
-	assert_emit_output(&emit_nested_dict, nested_object_json,
-	    nested_object_table);
-}
-TEST_END
-
 static void
 emit_types(emitter_t *emitter) {
 	bool b = false;
@@ -235,7 +252,17 @@ static const char *types_json =
 "\t\"k7\": 789,\n"
 "\t\"k8\": 10000000000\n"
 "}\n";
-
+static const char *types_json_compact =
+"{"
+	"\"k1\":false,"
+	"\"k2\":-123,"
+	"\"k3\":123,"
+	"\"k4\":-456,"
+	"\"k5\":456,"
+	"\"k6\":\"string\","
+	"\"k7\":789,"
+	"\"k8\":10000000000"
+"}";
 static const char *types_table =
 "K1: false\n"
 "K2: -123\n"
@@ -246,11 +273,6 @@ static const char *types_table =
 "K7: 789\n"
 "K8: 10000000000\n";
 
-TEST_BEGIN(test_types) {
-	assert_emit_output(&emit_types, types_json, types_table);
-}
-TEST_END
-
 static void
 emit_modal(emitter_t *emitter) {
 	int val = 123;
@@ -283,7 +305,18 @@ const char *modal_json =
 "\t\t\"i6\": 123\n"
 "\t}\n"
 "}\n";
-
+const char *modal_json_compact =
+"{"
+	"\"j0\":{"
+		"\"j1\":{"
+			"\"i1\":123,"
+			"\"i2\":123,"
+			"\"i4\":123"
+		"},"
+		"\"i5\":123,"
+		"\"i6\":123"
+	"}"
+"}";
 const char *modal_table =
 "T0\n"
 "  I1: 123\n"
@@ -293,13 +326,8 @@ const char *modal_table =
 "    I5: 123\n"
 "  I6: 123\n";
 
-TEST_BEGIN(test_modal) {
-	assert_emit_output(&emit_modal, modal_json, modal_table);
-}
-TEST_END
-
 static void
-emit_json_arr(emitter_t *emitter) {
+emit_json_array(emitter_t *emitter) {
 	int ival = 123;
 
 	emitter_begin(emitter);
@@ -338,14 +366,24 @@ static const char *json_array_json =
 "\t\t]\n"
 "\t}\n"
 "}\n";
-
+static const char *json_array_json_compact =
+"{"
+	"\"dict\":{"
+		"\"arr\":["
+			"{"
+				"\"foo\":123"
+			"},"
+			"123,"
+			"123,"
+			"{"
+				"\"bar\":123,"
+				"\"baz\":123"
+			"}"
+		"]"
+	"}"
+"}";
 static const char *json_array_table = "";
 
-TEST_BEGIN(test_json_arr) {
-	assert_emit_output(&emit_json_arr, json_array_json, json_array_table);
-}
-TEST_END
-
 static void
 emit_json_nested_array(emitter_t *emitter) {
 	int ival = 123;
@@ -391,12 +429,27 @@ static const char *json_nested_array_json =
 "\t\t]\n"
 "\t]\n"
 "}\n";
-
-TEST_BEGIN(test_json_nested_arr) {
-	assert_emit_output(&emit_json_nested_array, json_nested_array_json,
-	    json_array_table);
-}
-TEST_END
+static const char *json_nested_array_json_compact =
+"{"
+	"["
+		"["
+			"123,"
+			"\"foo\","
+			"123,"
+			"\"foo\""
+		"],"
+		"["
+			"123"
+		"],"
+		"["
+			"\"foo\","
+			"123"
+		"],"
+		"["
+		"]"
+	"]"
+"}";
+static const char *json_nested_array_table = "";
 
 static void
 emit_table_row(emitter_t *emitter) {
@@ -443,18 +496,29 @@ emit_table_row(emitter_t *emitter) {
 static const char *table_row_json =
 "{\n"
 "}\n";
-
+static const char *table_row_json_compact = "{}";
 static const char *table_row_table =
 "ABC title       DEF title  GHI\n"
 "123                  true  456\n"
 "789                 false 1011\n"
 "\"a string\"          false  ghi\n";
 
-TEST_BEGIN(test_table_row) {
-	assert_emit_output(&emit_table_row, table_row_json, table_row_table);
-}
+#define GENERATE_TEST(feature)					\
+TEST_BEGIN(test_##feature) {					\
+	assert_emit_output(emit_##feature, feature##_json,	\
+	    feature##_json_compact, feature##_table);		\
+}								\
 TEST_END
 
+GENERATE_TEST(dict)
+GENERATE_TEST(table_printf)
+GENERATE_TEST(nested_dict)
+GENERATE_TEST(types)
+GENERATE_TEST(modal)
+GENERATE_TEST(json_array)
+GENERATE_TEST(json_nested_array)
+GENERATE_TEST(table_row)
+
 int
 main(void) {
 	return test_no_reentrancy(
@@ -463,7 +527,7 @@ main(void) {
 	    test_nested_dict,
 	    test_types,
 	    test_modal,
-	    test_json_arr,
-	    test_json_nested_arr,
+	    test_json_array,
+	    test_json_nested_array,
 	    test_table_row);
 }