# Link preview checker https://flaghand.com/link-preview-checker draws the card X and LinkedIn build for a link, from the page's own og: and twitter: tags and its image: X's large card or its small one, LinkedIn's thumbnail beside the title, on desktop or a phone, in light or dark, with what is missing or wrong for each and how each cuts the image. A free Twitter card validator and LinkedIn post inspector, no sign-up. Flaghand's server reads the page's head and its image once and keeps nothing: no copy, and no log of the address. ## How to use it 1. Paste the page's link and choose Check. 2. Read what to fix for X and for LinkedIn, and the tags the page has. 3. Switch between Desktop and Phone, Light and Dark, to see each card there. An agent can open it set up: https://flaghand.com/link-preview-checker#url=https://example.com/post&view=phone&theme=dark (view=desktop|phone, theme=light|dark), or call it directly: POST https://flaghand.com/api/link-preview with JSON {"url": "https://example.com/post"}. The answer has the page's tags, each image's size, the card each network draws and what to fix (https://flaghand.com/llms.txt has the fields). ## Questions. ### Is there still a Twitter card validator? X’s own Card Validator stopped showing previews in 2022. This page draws the card from the tags X reads: the large card or the small one, the title, the domain, and the image as X crops it. ### How is this different from LinkedIn Post Inspector? LinkedIn’s Post Inspector needs a LinkedIn sign-in and also refreshes LinkedIn’s copy of your page. This page needs no sign-in and shows LinkedIn’s card beside X’s, with what to fix for each. ### Why does X show the small card? The page has no twitter:card tag, its twitter:card is summary, or X couldn’t use its image. For the large card, set twitter:card to summary\_large\_image and use an image at least 300 × 157, under 5 MB. ### What image size works for link previews? 1200 × 630 (1.91:1), as a JPG, PNG, WebP or GIF under 5 MB. X’s large card shows it whole. LinkedIn’s thumbnail is 16:9, so it cuts 3% from each side: keep words away from the edges. ### I fixed my tags. Why do X and LinkedIn still show the old card? X keeps its copy of a page’s card for about a week, LinkedIn for 48 hours after the link was last shared. LinkedIn’s Post Inspector fetches a fresh one. On X, a link that differs, such as one with ?v=2 added, gets a new card. ### Do you keep the links I check? No. Flaghand’s server reads the page’s head and its image once, sends what it found to this page, and keeps nothing: no link is stored or logged. ### Can my agent check a link? Yes. POST {"url": "https://example.com/post"} to /api/link-preview on this site. The JSON answer has the page’s tags, its image’s size, the card each network draws and what to fix. ## Flaghand The cards here are drawn by Flaghand's own X and LinkedIn renderers, the ones its desk previews drafts with, so an owner approves the card people will see. Flaghand is X and LinkedIn posting for AI agents: your agent drafts through Flaghand's API, CLI or MCP server, you approve the exact preview with your passkey, and Flaghand posts exactly that. Sign up at https://app.flaghand.com/start. In a chat app, add the connector at https://app.flaghand.com/mcp: its sign-in page creates the account. An agent with a shell can start the sign-up for its person over HTTP (https://flaghand.com/llms.txt, Quickstart). For agents: https://flaghand.com/llms.txt (this site) and https://app.flaghand.com/llms.txt (the product's agent guide).