# Open Graph checker: test your link previews > Free Open Graph checker: preview any link on X, LinkedIn, Facebook and Slack, check the og:image size and get the tags to fix it. Canonical: https://productsfarm.com/tools/og-checker See how a link looks when it's shared on X, LinkedIn, Facebook and Slack, and what to fix. Free, no sign-up. Use it at [Open Graph checker](https://productsfarm.com/tools/og-checker). ## How it works 1. Paste the address of any public page. We read its HTML the way share crawlers do, without running JavaScript. 2. We fetch the share image and measure its size, shape, format and file size against the usual advice: 1200 × 630, under 5 MB. 3. You see the card each platform builds, what it falls back to when a tag is missing, what to fix and the tags to paste. ## Questions ### What are Open Graph tags? Meta tags in a page's head that tell apps what to show when someone shares the link: og:title, og:description, og:image and og:url. Facebook created them, and LinkedIn, Slack, X and most chat apps read them. ### What size should an og:image be? 1200 × 630 pixels, a 1.91:1 shape, as a PNG or JPG under 5 MB. Facebook shows images under 600 × 315 as a small thumbnail and skips images under 200 × 200. ### Do I need X tags if I have Open Graph tags? Only one: twitter:card. X reads og:title, og:description and og:image when its own tags are missing, but the card type comes from twitter:card. Set it to summary_large_image for the large image card. ### I fixed my tags. Why does X still show the old preview? X keeps a link's card for about 7 days. Sharing the URL with a new query string, such as ?v=2, makes X read the page again. ### How do I refresh a preview on LinkedIn or Facebook? LinkedIn also keeps a preview for about 7 days. Paste the URL into LinkedIn's Post Inspector to read the page again at once. On Facebook, use the Sharing Debugger and click Scrape again. ### Is it free? Yes, with no sign-up. You can run 30 checks an hour, and a page checked in the last 5 minutes shows its saved result. ## Related - [Free tools](https://productsfarm.com/tools)