diff --git a/src/lx/main.c b/src/lx/main.c
index 2c485ec59..f17007599 100644
--- a/src/lx/main.c
+++ b/src/lx/main.c
@@ -125,6 +125,7 @@ print_name(const char *name)
 		{ "test", NULL          },
 		{ "dot",  lx_print_dot  },
 		{ "dump", lx_print_dump },
+		{ "json", lx_print_json },
 		{ "zdot", lx_print_zdot },
 		{ "c",    lx_print_c    },
 		{ "h",    lx_print_h    }
diff --git a/src/lx/print.h b/src/lx/print.h
index 118ec208c..78b4c07b4 100644
--- a/src/lx/print.h
+++ b/src/lx/print.h
@@ -54,6 +54,7 @@ lx_print lx_print_c;
 lx_print lx_print_h;
 lx_print lx_print_dot;
 lx_print lx_print_dump;
+lx_print lx_print_json;
 lx_print lx_print_zdot;
 
 #endif
diff --git a/src/lx/print/Makefile b/src/lx/print/Makefile
index dc2e3f4ea..2304cc4ca 100644
--- a/src/lx/print/Makefile
+++ b/src/lx/print/Makefile
@@ -4,6 +4,7 @@ SRC += src/lx/print/c.c
 SRC += src/lx/print/h.c
 SRC += src/lx/print/dot.c
 SRC += src/lx/print/dump.c
+SRC += src/lx/print/json.c
 SRC += src/lx/print/zdot.c
 
 .for src in ${SRC:Msrc/lx/print/*.c}
diff --git a/src/lx/print/json.c b/src/lx/print/json.c
new file mode 100644
index 000000000..d1c61f07c
--- /dev/null
+++ b/src/lx/print/json.c
@@ -0,0 +1,163 @@
+/*
+ * Copyright 2019 Jamey Sharp
+ *
+ * See LICENCE for the full copyright terms.
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include <adt/set.h>
+
+#include <fsm/fsm.h>
+#include <fsm/pred.h>
+
+#include "libfsm/internal.h" /* XXX */
+
+#include "lx/ast.h"
+#include "lx/print.h"
+
+/* TODO: centralise with libfsm */
+static unsigned int
+indexof(const struct fsm *fsm, const struct fsm_state *state)
+{
+	struct fsm_state *s;
+	unsigned int i;
+
+	assert(fsm != NULL);
+	assert(state != NULL);
+
+	for (s = fsm->sl, i = 0; s != NULL; s = s->next, i++) {
+		if (s == state) {
+			return i;
+		}
+	}
+
+	assert(!"unreached");
+	return 0;
+}
+
+static unsigned int
+zindexof(const struct ast *ast, const struct ast_zone *zone)
+{
+	struct ast_zone *z;
+	unsigned int i;
+
+	assert(ast != NULL);
+	assert(zone != NULL);
+
+	for (z = ast->zl, i = 0; z != NULL; z = z->next, i++) {
+		if (z == zone) {
+			return i;
+		}
+	}
+
+	assert(!"unreached");
+	return 0;
+}
+
+static int
+print_zone(FILE *f, const struct ast *ast, const struct ast_zone *z)
+{
+	struct fsm_state *s, *st;
+	int ret;
+
+	assert(f != NULL);
+	assert(z != NULL);
+	assert(z->fsm != NULL);
+	assert(fsm_all(z->fsm, fsm_isdfa));
+	assert(ast != NULL);
+
+	fprintf(f, "    {\n");
+	fprintf(f, "      \"initial_state\": %u,\n", indexof(z->fsm, z->fsm->start));
+	fprintf(f, "      \"states\": [\n");
+
+	for (s = z->fsm->sl; s != NULL; s = s->next) {
+		struct fsm_edge *e;
+		struct set_iter it;
+
+		fprintf(f, "        {\n");
+
+		e = set_first(s->edges, &it);
+
+		if (fsm_isend(z->fsm, s)) {
+			const struct ast_mapping *m = s->opaque;
+			assert(m != NULL);
+
+			if (m->token != NULL) {
+				fprintf(f, "          \"token\": \"$%s\",\n", m->token->s);
+			}
+			if (m->to != NULL) {
+				fprintf(f, "          \"next_zone\": %u,\n", zindexof(ast, m->to));
+			}
+
+			fprintf(f, "          \"accepts\": true%s\n", e != NULL ? "," : "");
+		}
+
+		if (e != NULL) {
+			int first = 1;
+			fprintf(f, "          \"transitions\": [");
+			for (; e != NULL; e = set_next(&it)) {
+				struct set_iter jt;
+				for (st = set_first(e->sl, &jt); st != NULL; st = set_next(&jt)) {
+					fprintf(f, "%s\n            { \"symbol\": %u, \"target\": %u }",
+						first ? "" : ",",
+						e->symbol,
+						indexof(z->fsm, st));
+					first = 0;
+				}
+			}
+			fprintf(f, "\n          ]\n");
+		}
+
+		fprintf(f, "        }%s\n", s->next ? "," : "");
+	}
+
+	fprintf(f, "      ]\n");
+	fprintf(f, "    }%s\n", z->next ? "," : "");
+
+	return 0;
+}
+
+void
+lx_print_json(FILE *f, const struct ast *ast)
+{
+	const struct ast_zone *z;
+	unsigned int zn;
+
+	assert(f != NULL);
+
+	for (z = ast->zl; z != NULL; z = z->next) {
+		if (!fsm_all(z->fsm, fsm_isdfa)) {
+			errno = EINVAL;
+			return;
+		}
+	}
+
+	fprintf(f, "{\n");
+	fprintf(f, "  \"prefix\": { \"api\": \"%s\", \"tok\": \"%s\", \"lx\": \"%s\" },\n",
+		prefix.api, prefix.tok, prefix.lx);
+	fprintf(f, "  \"initial_zone\": %u,\n", zindexof(ast, ast->global));
+	fprintf(f, "  \"zones\": [\n");
+
+	if (print_progress) {
+		zn = 0;
+	}
+
+	for (z = ast->zl; z != NULL; z = z->next) {
+		if (print_progress) {
+			if (important(zn)) {
+				fprintf(stderr, " z%u", zn);
+			}
+			zn++;
+		}
+
+		if (-1 == print_zone(f, ast, z)) {
+			return; /* XXX: handle error */
+		}
+	}
+
+	fprintf(f, "  ]\n");
+	fprintf(f, "}\n");
+}