Enter a URL and we fetch the page on our server, list and grade its og: / twitter: tags, and reproduce how the card will look on X and Facebook. The og:image is not just read from the markup — we fetch it and check its real format and dimensions.
Generating the tags is the job of the OGP meta tag wizard on First CH Tools (fully in-browser). Browsers cannot fetch another site's URL directly (CORS), so this server-side app takes over the checking half.
Need to generate tags? OGP meta tag wizard (tools.first-ch.com, in-browser)Sent: only the URL you type. Our server (Cloudflare Workers) fetches that URL as a public page, then fetches the single og:image it declares.
Stored: nothing. The check lives entirely inside one request and writes neither the URL nor the result to any database (no KV, no D1). It leaves memory when the request ends.
Returned: the tag values we found, their grades, and the image's format and size. We never re-serve the fetched HTML or image (preview images are loaded by your browser directly from the source site).
Note: public GET only. URLs pointing at internal networks, localhost or private IPs are rejected, and pages behind a login cannot be checked.
POST /ogp-check/api/inspect with JSON ({"url": "https://example.com/"}) or a form body and you get the same report back as JSON.
Every platform keeps its own cache. After fixing tags, confirm with the official tools as well (X Card Validator, Facebook Sharing Debugger).