Check My OG
See how a link will preview before you share it. checkmyog.com
Most link-preview checkers read your tags and stop. This one fetches the page the way Twitterbot and facebookexternalhit do, then downloads the files the tags point at and checks them: whether og:image is a real 1.91:1 image the right size, whether og:video is H.264, yuv420p, faststart, served as video/mp4 with range requests and small enough for iMessage. It then tells you which apps will play the video and which will show the poster, with a source for each claim. og:video is optional: a page without one is noted, not failed, because most pages have none and only iMessage and Discord ever play one.
Short version of what it has found so far: iMessage autoplays og:video, Discord shows it with a play button, and everyone else (X, Facebook, LinkedIn, Slack, WhatsApp, Telegram, Bluesky, Mastodon, Signal, Matrix) shows og:image, so that image matters most. X also covers its bottom-left corner with the domain, so keep text and logos out of there. Without og:image, iMessage and the Facebook crowd fall back to the page title in a text-only card; with no og tags at all, Discord and X show nothing but the link. The current list with sources is in public/support.json.
Use it
- In a browser:
https://checkmyog.com/?url=https://example.com/
- Markdown report (good for pasting into a model):
curl -s "https://checkmyog.com/api/inspect?url=https://example.com/&format=md"
- JSON:
curl -s "https://checkmyog.com/api/inspect?url=https://example.com/"
- Pages to test an app with:
https://checkmyog.com/ itself passes every check, and so does https://thisisaridiculouslylongdomainnamemadeonlytotestyourlinkpreviews.international/, a 77-character domain (the longest label the DNS allows) served by this same app, for seeing what an app does with a very long name. The example pills under the URL box run these.
No key and no sign-in, 20 checks a minute per IP. llms.txt explains the API for agents and openapi.json describes it.
Run it yourself
It is one Python file using only the standard library, plus ffprobe from ffmpeg.
python3 server.py # http://localhost:8080
python3 -m unittest discover -s tests
Or with Docker: docker build -t checkmyog . && docker run -p 8080:8080 checkmyog
| Variable | Default | What it does |
|---|
PORT | 8080 | Port to listen on |
PUBLIC_URL | https://checkmyog.com | Base URL written into the page, llms.txt and openapi.json |
POSTHOG_KEY | unset | PostHog project key. Unset means no analytics at all |
POSTHOG_HOST | https://us.i.posthog.com | PostHog ingest host |
CLIENT_IP_HEADER | Fly-Client-IP | Header your proxy sets with the client IP, used for rate limiting. Set it empty if nothing in front of the server sets one |
How it works
server.py serves public/ and one endpoint, /api/inspect. The page in public/index.html calls that endpoint, draws the previews and runs a few checks in your own browser (can it decode the video, does the poster load, does the fallback work).
The server fetches URLs that anyone types in, so it guards against SSRF: every hop, redirects included, resolves the host, refuses private, loopback, link-local and reserved addresses, and connects to the IP it checked, so DNS can't be rebound between the check and the request. Only http and https on ports 80 and 443. Downloads are size-capped and there is a per-IP rate limit.
Privacy
The hosted site at checkmyog.com uses cookieless PostHog analytics (no cookies, no banner) and records each URL that gets checked, through the page or the API. Visitors are counted with a daily hash, not a stored IP. If you'd rather nothing be recorded, run your own copy; with POSTHOG_KEY unset it sends nothing anywhere.
Contributing
Issues and pull requests are welcome, from people and from AI agents. If an app previews a link differently than this tool says, that is the most useful issue you can file. See CONTRIBUTING.md.
License
MIT. Made by Dayward AI.
