About this tool
Twitter/X's web-based card validator is gone, and Facebook's Sharing Debugger requires a Facebook login, so there's surprisingly no quick way to check whether your OGP and Twitter Card tags are set up correctly. This tool works from HTML you paste yourself — no login, no URL fetch, just a preview and a list of issues.
You can paste the HTML straight from your browser's "View Page Source" — a full document or just the <head> fragment both parse the same way.
Parsing happens entirely in your browser using the built-in DOMParser API — nothing is sent to a server. The only exception is if you turn on "Load image", which fetches the referenced image URL directly to check its real size.
How to use it
- Open the target page and use "View Page Source" (or right-click → View Source) to see its HTML.
- Copy all of it and paste it into the text box.
- Twitter/X and Facebook/LINE-style card previews, along with any detected issues, appear on the right.
- Turn on "Load image" if you also want to confirm the real dimensions of the referenced image.
Features
No login required
Unlike Facebook's Sharing Debugger, there's no login step — just paste your HTML and check the result.
Two previews at once
See a Twitter/X card and a general OGP-style card (Facebook, LINE, and similar) side by side.
Automatic detection of missing tags and overlong text
Flags missing required tags, an overlong title or description, duplicate tags, and more automatically.
Optional real image size check
Turn on "Load image" to fetch the referenced image URL and see its real dimensions. Off by default.
Frequently asked questions
Can't I just enter a URL instead of pasting HTML?
This site is served as a fully static site with no server-side URL fetching, so fetching an arbitrary URL directly from the browser fails on most sites due to CORS. That's why you paste the page's HTML yourself instead.
Is it safe to always leave "Load image" turned on?
It's safe, but since it directly accesses the referenced image URL, it's off by default. When enabled, your browser fetches the image URL directly to display its real size.
Is the LINE or Slack preview pixel-accurate?
The "Preview on Facebook, LINE, etc." card is a general approximation of the layout shared by most OGP-consuming services. It isn't an exact per-service reproduction.
Is the HTML I paste sent anywhere?
No. Parsing happens entirely in your browser via the built-in DOMParser API. The only network access is when you turn on "Load image", which fetches the referenced image URL.