diff --git a/crates/engine/src/media_browser.rs b/crates/engine/src/media_browser.rs
index 5edd67ca..12c002d2 100644
--- a/crates/engine/src/media_browser.rs
+++ b/crates/engine/src/media_browser.rs
@@ -312,7 +312,9 @@ pub fn footage_metadata(f: &Footage) -> Value {
         "pixelAspect": f.pixel_aspect,
         "frameRate": f.frame_rate.as_f64(),
         "duration": f.duration.seconds(),
-        "frames": if f.has_video && f.kind != FootageKind::Still { Some(f.frame_rate.frame_at(f.duration)) } else { None },
+        // Rounded like the media pool's frame count: Matroska stores the duration in whole
+        // milliseconds, a hair short of the last frame at 30 fps (#1429).
+        "frames": if f.has_video && f.kind != FootageKind::Still { Some(f.frame_rate.frame_at(f.frame_rate.snap_nearest(f.duration))) } else { None },
         "hasVideo": f.has_video,
         "hasAudio": f.has_audio,
         "alpha": format!("{:?}", f.alpha),
diff --git a/crates/host/tests/webm_metadata.rs b/crates/host/tests/webm_metadata.rs
new file mode 100644
index 00000000..2e3fed9d
--- /dev/null
+++ b/crates/host/tests/webm_metadata.rs
@@ -0,0 +1,28 @@
+//! A WebM rendered by EffectCraft and imported back reports its real frame count (#1429). Matroska
+//! stores the duration in whole milliseconds, so at 30 fps a 1-frame file lasts 33 ms, just short
+//! of one 33.33 ms frame.
+
+use serde_json::json;
+
+fn tmp(name: &str) -> String {
+    let d = std::env::temp_dir().join(format!("effectcraft-host-webm-meta-{}", std::process::id()));
+    std::fs::create_dir_all(&d).unwrap();
+    d.join(name).to_string_lossy().to_string()
+}
+
+#[test]
+fn a_webm_at_30_fps_reports_every_frame() {
+    for n in [1u32, 4] {
+        let mut s = effectcraft_host::session();
+        let out = tmp(&format!("frames-{n}.webm"));
+        s.execute("comp.new", json!({"name": "Main", "width": 64, "height": 36, "frameRate": 30, "duration": 1})).unwrap();
+        s.execute("layer.newSolid", json!({"name": "BG", "color": "#142850"})).unwrap();
+        let span = json!({"comp": "Main", "format": "webm", "output": out, "timeSpan": "custom", "start": 0, "duration": n as f64 / 30.0});
+        s.execute("renderQueue.add", span).unwrap();
+        s.execute("renderQueue.render", json!({"wait": true})).unwrap();
+        let r = s.execute("file.import", json!({"paths": [out.clone()]})).unwrap();
+        let m = s.execute("item.metadata", json!({"item": r["items"][0]})).unwrap();
+        let _ = std::fs::remove_file(&out);
+        assert_eq!(m["item"]["frames"], json!(n), "{n} rendered frames: {m}");
+    }
+}