Link preview checker
Paste an address and see the card it makes on X, on Facebook and LinkedIn, in Slack and iMessage, and in a Google result, drawn from the page's own Open Graph and Twitter Card tags. Anything missing or wrong is listed with the fix.
Under it: what the tags are, which one each platform reads, the image sizes that work everywhere, how long a title and a description can be, why a platform keeps showing an old card, and how the same page would look as a listing on the board.
What the tags are
When a link is pasted into a feed, a chat or a message, the platform fetches the page and looks in its head for a handful of meta tags that say what to show: a title, a description, an image, and the address the card should point at. The Open Graph tags, written og:title and so on, were defined by Facebook and are read by nearly every platform. Twitter Card tags, written twitter:card and so on, are read by X and fall back to Open Graph when absent.
With the tags in place a link is a card with a picture, and it is clicked. Without them it is a bare address, or a card built from whatever the platform guessed, which is usually the wrong picture and a title cut off mid-sentence.
Which tag each platform reads
| Platform | Title | Description | Image | Notes |
|---|---|---|---|---|
| og:title | og:description | og:image | Caches a card for weeks; refresh it in the Sharing Debugger | |
| og:title | og:description | og:image | Caches for about a week; refresh in the Post Inspector | |
| X | twitter:title, then og:title | twitter:description, then og:description | twitter:image, then og:image | twitter:card decides the shape: summary_large_image for the wide card |
| Slack | og:title | og:description | og:image | Also reads twitter tags; shows a compact card |
| iMessage | og:title | not shown | og:image, then the site icon | Falls back to the apple-touch-icon when there is no image |
| Discord | og:title | og:description | og:image | Reads theme-color for the card's edge |
| the title tag | meta description | not from these tags | A search result is built from the page, not the card |
The checker draws four of these and reads all of them. A page with the four Open Graph tags and a twitter:card tag is right on every platform in the table.
The image that works everywhere
- 1200 by 630 pixels, which is a ratio of 1.91 to 1. Facebook, LinkedIn, X's large card, Slack and Discord all crop to it or show it whole.
- At least 600 pixels wide. Below that Facebook shows a small square thumbnail beside the text instead of the wide card.
- Under about 5 megabytes, as a JPEG, PNG or WebP. Some platforms refuse a larger file and show nothing.
- An absolute https address, not a relative path. Several platforms will not resolve a relative one.
- Nothing important in the outer ten percent. Every platform crops a little differently, and text against the edge is text that is cut.
The checker fetches the image and reports its real size, which is not always the size the page thinks it has.
How long the title and description can be
A title is cut at about sixty characters on most cards and at about seventy in a search result. A description is cut at about a hundred and fifty characters on the cards that show one, and at about a hundred and sixty in a search result. The checker counts both and says where the cut lands.
Write the title as a claim, not a label, because the card is competing with the post around it. Write the description as the second sentence of the same thought. A description that repeats the title is a card that says one thing twice and leaves the second line empty.
Why a platform keeps showing the old card
Every platform caches the card it made the first time a link was shared, and a fixed tag does not clear it. Facebook's Sharing Debugger, LinkedIn's Post Inspector and X's Card Validator each fetch the page again and replace the cached card. Slack and Discord refetch on their own within a day or so. Changing the address, even by a query parameter, produces a fresh card everywhere at once.
The checker never caches. What it shows is what the page says right now, which is also what a platform will see the next time it fetches.
The same page as a listing on The Board
A listing on the board is a mark, a name, one line and a link, which is about what a share card is. The last preview under the checker draws the page as a listing: the site's icon or a monogram as the mark, the site name or the title as the brand, the description trimmed to one line, and the host as the link. It is a fair picture of what a spot here would look like, drawn from what the page already says about itself.
The real listing lets you choose all four, and changing any of them is free and never touches what the listing paid.
Questions people ask about a link preview checker
Why does my link not show a preview?
What size should an Open Graph image be?
How do I refresh a link preview on Facebook or LinkedIn?
What is the difference between Open Graph and Twitter Cards?
How long can an Open Graph title be?
Does the checker cache results?
Can I check a page that is not live yet?
Why does X show a small card instead of a large one?
More free tools
All of them are on the free tools page. Every one is free, asks for no account, and stores nothing of yours on our side. A listing on The Board is a logo, a line and a link, from $1, and every number on the board is public.