Help Centre

Why does my link show no preview image on Slack / LinkedIn / Twitter?

This is the most common issue Previewcard catches. The usual causes are:

• Relative og:image URL. If your og:image is set to something like /images/hero.jpg instead of https://example.com/images/hero.jpg, the platform cannot resolve it and shows nothing. Previewcard flags this explicitly.
• The image returns a 404. The tag might point at a URL that no longer exists. Previewcard fetches the image URL and reports the HTTP status.
• The image is too small. Most platforms require a minimum of 600×315 pixels; 1200×630 is the recommended size. A 200×200 logo image will be rejected silently.
• Missing tags entirely. If the page has no og:title or og:image, the platform falls back to the page <title> or nothing at all. Previewcard shows exactly which tags are present and which are missing.

How to fix: Check the URL in Previewcard first. It will list every issue under Issues Found. Fix each one on your page, then re-check.

What tags does Previewcard check?

Previewcard parses the page for the following meta tags and presents each with its value and presence status:

Open Graph (used by Facebook, LinkedIn, and as fallback by others):

• og:title — The title shown in the social card.
• og:description — The description text.
• og:image — The preview image URL.
• og:url — The canonical URL.
• og:site_name — The site or publisher name.
• og:locale — Language/locale tag.
• og:type — Content type (website, article, etc.).

Twitter Card (used by X/Twitter):

• twitter:card — Card type (summary, summary_large_image, etc.).
• twitter:title — Title for Twitter (falls back to og:title if missing).
• twitter:description — Description (falls back to og:description).
• twitter:image — Image URL for Twitter (falls back to og:image).
• twitter:site — Twitter handle of the publisher.

Previewcard also reports which fallback chains each platform uses — for example, whether Twitter will use og:title when twitter:title is absent, or whether LinkedIn will show a description when only og:description is set.

What size should my og:image be?

There is no single answer — each platform has different requirements. The safe, universal recommendation is 1200×630 pixels at a 1.91:1 aspect ratio.

Here is what the major platforms expect:

• Facebook: At least 600×315 pixels, ideally 1200×630. Ratio close to 1.91:1. Max file size 8 MB.
• LinkedIn: At least 600×315 pixels, ideally 1200×630. Uses the same og:image as Facebook.
• Twitter/X: For summary_large_image cards, at least 300×157 (but 1200×630 recommended). Twitter falls back to og:image when twitter:image is not set, but may crop differently.
• Slack: Uses Open Graph tags. Image minimum is around 200×200, but 1200×630 produces the best results.

Previewcard fetches the image, reads its real dimensions, and compares them against each platform's known minimums. A 200×200 image will be flagged as too small for Facebook but may pass for Slack.

I fixed the tags on my page but the shared link still looks broken — why?

Social platforms cache preview cards. When a URL is shared, the platform fetches the page once and stores the card metadata for hours or days. Fixing the tags on your page does not retroactively update every share — the old card is cached.

How to force a refresh:

• Facebook: Use the Facebook Sharing Debugger — paste your URL and click Scrape Again.
• LinkedIn: Use the LinkedIn Post Inspector — paste your URL and click Inspect.
• Twitter/X: There is no official debugger. Twitter typically re-fetches cards within 24–48 hours. You can append a query parameter (e.g. ?v=2) to force a fresh fetch.
• Slack: Slack re-fetches link previews after a few minutes. Pasting the same URL again may not retrigger — try a unique URL or un-furl/re-furl via the message menu.

Always confirm your tags are correct first with Previewcard, then use the platform tools above to refresh the cached version.

Does Previewcard store the URLs I check?

No. Previewcard is a stateless diagnostic tool:

• URLs you submit are sent via an HTTP POST to our server, processed in memory, and discarded immediately after the response is sent.
• We do not store check results, URLs, IP addresses, or any identifying information in a database, log, or cache.
• No cookies, no tracking pixels, no persistent identifiers.
• No accounts, no sessions, no signup — there is nothing to log in to.

See the Privacy Policy for full details.

The app says "The API may not be deployed yet" — is it working?

The previewcard web app sends check requests to a backend API. If that error message appears, it means the Cloudflare Worker (or server-side handler) that processes URL checks has not been deployed yet, or is not responding to requests.

What this means: The frontend (the form, the results display, the diagnostic layout) is complete and working in the browser. The backend — the part that actually fetches a URL and parses its tags — needs to be deployed separately.

What to do: The owner needs to deploy the check API before the tool will return results. Once the API is live, simply refresh the app page and submit a URL — no code changes needed on the frontend.

This is a known limitation — it is not an issue with your page or your URL. See the Known limitations section below for the full list of what is not yet built.