github-video-embed skill

github-video-embed

The reader should press play inside the same .md file, without leaving the page, and anyone with access to the repository should see the player. GitHub renders an inline <video> player only for a GitHub-hosted attachment URL.

The rule

Put a bare https://github.com/user-attachments/assets/<uuid> on its own line in the .md. GitHub turns it into a <video> player.

These render blank or get stripped:

• a raw committed-file URL (.../raw/...)
• a release asset URL (releases/download/...)
• a <video src="..."> tag pointing at either of them

Committing the .mp4 under docs/ is still worth doing as the source of truth, but it is not what the page shows.

Getting the attachment URL

The upload needs a signed-in browser session. A personal access token cannot do it: the upload policy endpoint (/upload/policies/assets) answers 422.

1. Export your own signed-in browser session's GitHub cookies, used once for this upload and shredded afterwards. Include _gh_sess: it is a session cookie held only in browser memory, never in the cookie database on disk, so take it from the live browser, not from the profile folder.
2. Start a Chromium browser headless with --remote-debugging-port and a temporary --user-data-dir, and drive it over the DevTools protocol (Node 22 and later have a global WebSocket, so no extra package is needed).
3. Call Network.setCookie for every cookie, keeping its domain, path, secure, httpOnly and sameSite values, then navigate to GitHub. Check that meta[name=user-login] shows the expected account.
4. Open a classic Markdown editor page: the release notes editor (/releases/edit/<tag>), a wiki page, or a commit comment. Not /issues/new: that page mounts its editor late and exposes no file input headless. The release editor has a plain textarea[name="release[body]"] and an input[type=file].
5. Call DOM.setFileInputFiles with every file on that input[type=file], then poll the textarea until the user-attachments/assets/<uuid> URLs appear. The upload happens at once. Do not save or submit the form: the release stays unchanged, but the file is already uploaded, and in a public repository its URL works without signing in. Do not use this for a video that must stay private until a later date.
6. Put each bare URL on its own line in the doc, then commit and push.

There is no bundled uploader; the steps above are the recipe.

Verify, then scrub

Fetch the rendered page with the same session and count the players:

curl -s -b "$COOKIE_JAR" "https://github.com/$OWNER/$REPO/blob/$BRANCH/$DOC_PATH" | grep -o '<video' | wc -l

The count must equal the number of videos. Then delete the cookie export with shred -u (or your platform's secure delete) and remove the temporary --user-data-dir: both hold a live session.

Alternative

A self-contained HTML page with the videos inlined as data: URIs plays anywhere with no upload. It only reaches the people you send it to, so it does not suit docs that a whole team reads in the repository.