diff --git a/include/mrk/ast.h b/include/mrk/ast.h
index 6d924cd..fc7f090 100644
--- a/include/mrk/ast.h
+++ b/include/mrk/ast.h
@@ -6,8 +6,6 @@
 
 #include "mrk/common.h"
 
-#define MRK_AST_NODE_ARGS 4
-
 typedef enum mrk_ast_node_type {
   mrk_ast_node_type_none = 0,
   mrk_ast_node_type_header,
@@ -48,4 +46,9 @@ mrk_err mrk_ast_node_init(mrk_ast_node **out);
  */
 mrk_err mrk_ast_node_child_append(mrk_ast_node **out, mrk_ast_node *parent);
 
+/**
+ * Output the AST as valid HTML
+ */
+mrk_err mrk_ast_to_html(char **out, const char *orig, mrk_ast_node *root);
+
 #endif
diff --git a/src/ast.c b/src/ast/ast.c
similarity index 100%
rename from src/ast.c
rename to src/ast/ast.c
diff --git a/src/ast/html.c b/src/ast/html.c
new file mode 100644
index 0000000..e3a66f4
--- /dev/null
+++ b/src/ast/html.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+
+#include "mrk/ast.h"
+#include "mrk/buf.h"
+
+mrk_err __mrk_ast_to_html(mrk_buf *buf, const char *orig, mrk_ast_node *root) {
+
+  for (size_t i = 0; i < root->children.len; i++) {
+    mrk_ast_node *child = root->children.arr[i];
+
+    switch (child->type) {
+    case mrk_ast_node_type_text:
+      // TODO replace certain characters with escape sequences
+      MRK_RES(mrk_buf_append_n(buf, orig + child->d.text.start,
+                               child->d.text.end - child->d.text.start));
+      break;
+    case mrk_ast_node_type_header: {
+      char tag[6];
+
+      sprintf(tag, "<h%lu>", child->d.header.depth);
+      MRK_RES(mrk_buf_append_n(buf, tag, 4));
+
+      MRK_RES(__mrk_ast_to_html(buf, orig, child));
+
+      sprintf(tag, "</h%lu>", child->d.header.depth);
+      MRK_RES(mrk_buf_append_n(buf, tag, 5));
+    } break;
+    case mrk_ast_node_type_space:
+      MRK_RES(mrk_buf_append_n(buf, " ", 1));
+      break;
+    case mrk_ast_node_type_link: {
+      size_t url_len = child->d.link.url_end - child->d.link.url_start;
+
+      // <a href="[url]">
+      char tag[12 + url_len];
+
+      sprintf(tag, "<a href=\"%.*s\">", (int)url_len,
+              orig + child->d.link.url_start);
+      MRK_RES(mrk_buf_append_n(buf, tag, 11 + url_len));
+
+      MRK_RES(__mrk_ast_to_html(buf, orig, child));
+
+      MRK_RES(mrk_buf_append_n(buf, "</a>", 4));
+    } break;
+    case mrk_ast_node_type_paragraph:
+      MRK_RES(mrk_buf_append_n(buf, "<p>", 3));
+      MRK_RES(__mrk_ast_to_html(buf, orig, child));
+      MRK_RES(mrk_buf_append_n(buf, "</p>", 4));
+      break;
+    case mrk_ast_node_type_none:
+      break;
+    }
+  }
+
+  return mrk_err_ok;
+}
+
+mrk_err mrk_ast_to_html(char **out, const char *orig, mrk_ast_node *root) {
+  mrk_buf buf;
+  MRK_RES(mrk_buf_init(&buf));
+
+  MRK_RES(__mrk_ast_to_html(&buf, orig, root));
+  MRK_RES(mrk_buf_compact(&buf));
+
+  *out = buf.s;
+
+  return mrk_err_ok;
+}