diff --git a/include/clap/all.h b/include/clap/all.h
index 54bbfbc4..b7ba57ac 100644
--- a/include/clap/all.h
+++ b/include/clap/all.h
@@ -13,3 +13,4 @@
 #include "ext/draft/tuning.h"
 #include "ext/draft/undo.h"
 #include "ext/draft/scratch-memory.h"
+#include "ext/draft/web.h"
diff --git a/include/clap/ext/draft/web.h b/include/clap/ext/draft/web.h
new file mode 100644
index 00000000..2d294ae6
--- /dev/null
+++ b/include/clap/ext/draft/web.h
@@ -0,0 +1,52 @@
+#pragma once
+
+static CLAP_CONSTEXPR const char CLAP_EXT_WEB[] = "clap.web/1";
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/// @page Web
+///
+/// This extension enables the plugin to provide the start-page for a webview UI, and exchange
+/// messages back and forth.
+///
+/// Messages are received in the webview using a standard MessageEvent, with the data in an
+/// ArrayBuffer. They are posted back to the plugin using window.parent.postMessage(), with the
+/// data in an ArrayBuffer or TypedArray.
+
+typedef struct clap_plugin_web {
+   // Returns the URL for the webview's initial navigation, as a null-terminated UTF-8 string.
+   // If this URL is relative, it is resolved relative to the plugin (bundle) directory, and
+   // cannot be outside it.  The host may use any protocol to serve this content, and the page
+   // must not assume that the root of the domain is the root of the bundle. The URL may also be
+   // absolute, including a `file://` URL.
+   // Returns true on success.
+   // [main-thread]
+   bool(CLAP_ABI *get_start)(const clap_plugin_t *plugin,
+                             char                *out_buffer,
+                             uint32_t            out_buffer_capacity);
+
+   // Receives a single message from the webview.
+   // Returns true on success.
+   // [main-thread]
+   bool(CLAP_ABI *receive)(const clap_plugin_t *plugin, const void *buffer, uint32_t size);
+
+} clap_plugin_web_t;
+
+typedef struct clap_host_web {
+   // Checks whether the webview is open (and ready to receive messages)
+   // [thread-safe]
+   bool(CLAP_ABI *is_open)(const clap_host_t *host);
+
+   // Sends a single message to the webview.
+   // It must not allocate or block if called from the audio thread.
+   // Returns true on success.
+   // [thread-safe]
+   bool(CLAP_ABI *send)(const clap_host_t *host, const void *buffer, uint32_t size);
+
+} clap_host_web_t;
+
+#ifdef __cplusplus
+}
+#endif