How the link preview checker works
What it reads
The server fetches your page with a normal browser-style user agent and parses og:title, og:description, og:image (and its width, height, alt and type), og:url, og:type, og:site_name, the twitter:card family, the canonical link, icon links, oEmbed alternate links and the HTML title.
For the image it uses the declared og:image:width and height if present. Otherwise it asks the image server for headers only to learn the content type and file size, using the same address checks. Real pixel dimensions are not measured when the page does not declare them.
Sources
Open Graph protocol: ogp.me. X Cards overview: developer.x.com, X for Websites, Cards. Facebook sharing guidance for webmasters: developers.facebook.com, Sharing. oEmbed specification: oembed.com. Checked October 2026.
The 1200 by 630 image size and the 60 character title point are widely used recommendations rather than hard limits, so they are marked as guidance in the checklist.
Limitations
The card mockups approximate each network layout. Real cards change with app versions, light and dark mode, and screen width, and a few networks apply their own rules (for example cropping) that no tag can control.
Pages that build their tags with JavaScript after loading, or that block automated requests or require a login, may look empty here even if a network with a special crawler sees more. If so, the server-rendered HTML is what to fix.
Frequently asked questions
Why does my link show no image or the wrong image when shared?
Usually the page has no og:image tag, the image URL is relative or blocked, or the network cached an older version of the page. This checker shows the exact og:image it finds, whether it loads, its type and size, and flags the common causes.
What image size should I use for link previews?
A 1200 by 630 pixel image (about a 1.91 to 1 ratio) is the commonly recommended size for large link cards, and it also suits the X summary_large_image card. Smaller images may show as a small thumbnail. Declare og:image:width and og:image:height so crawlers can lay the card out immediately.
What is the difference between Open Graph tags and Twitter Card tags?
Open Graph is a protocol (ogp.me) used by Facebook, LinkedIn, Slack and many other apps. Twitter Card tags are X-specific. X reads Open Graph tags when twitter tags are missing, but twitter:card is what chooses between the small summary card and the large image card.
How long should an og:title be?
Around 60 characters is where titles start to be cut off with an ellipsis in many cards. The exact point varies by network and screen, so the checker treats 60 as an approximate guide and warns above it.
How do I get a network to refresh a cached link preview?
Fix the tags first. Facebook has a Sharing Debugger that re-scrapes a URL on request. Other networks refresh on their own schedule, and adding a harmless query string to the shared link is a common way to get a fresh card. This tool always reads the live page and never uses a cache.
Is it safe to enter any URL?
The checker fetches only public http and https addresses. It refuses private, loopback, link-local and cloud-metadata addresses, follows at most 3 redirects, checking each one, reads at most 1 MB, and gives up after 5 seconds. It returns only the parsed fields, never the raw page.