How Previewcard works and what it tells you.

Previewcard renders a preview for LinkedIn, Facebook, Slack, and Twitter. Each platform reads a different combination of tags:

LinkedIn and Facebook primarily read Open Graph (og:*) tags. Twitter reads Twitter Card (twitter:*) tags first, with fallback to Open Graph when a Twitter-specific tag is missing. Slack reads the same Open Graph tags but applies its own minimum image size requirements.

The report tells you, per platform, exactly which tag was used for each field.

Previewcard does three things the raw tag values do not tell you:

Resolves relative image URLs. An og:image value like /images/share.png is resolved against the page URL. The raw value and the resolved URL are both shown.

Fetches the image and reports its real dimensions. A tag pointing at a 404 or an image that is 200×200 when the platform wants 1200×630 produces a broken card. Previewcard actually fetches the image, reads its width and height from the file header, and flags values outside the platform's recommended range.

Checks HTTP status. An image that returns a 404 or a redirect to a login page is flagged as unresolvable.

Each platform has a recommended minimum image dimension:

LinkedIn / Facebook: Minimum 1200×630 pixels (a 1.91:1 aspect ratio). Images smaller than this will appear cropped or stretched when shared.

Twitter (summary card with large image): Minimum 300×157 pixels, but 1200×600 is recommended for best display.

Slack: Minimum 200×200 pixels for the image to appear at all.

If your image is flagged, you need to update the og:image (and optionally twitter:image) on your page to point at a larger asset. Just resizing the existing image file is usually enough.

Previewcard checks the URL you submit by fetching it. If the page returned an error (4xx or 5xx status), or the fetch timed out, or the page is hosted on Cloudflare's own network (a platform-level restriction), Previewcard reports the page as not fetchable.

This is a limitation of the checking tool, not a finding about your tags. When a page cannot be fetched, no tag analysis is possible, and the report says that clearly — it never substitutes a guess for what the tags contain.

No. Previewcard is stateless. Each check is processed and the result exists only in your browser session. Refreshing the page discards it. There is no user account, no saved history, no email sender, and no scheduled re-check capability.

If you need a record of a result, take a screenshot or copy the details before navigating away. This is an honest limitation — saying "we will save it" when there is no storage would be worse than saying we do not.

No. Previewcard is free and does not require an account or any personal information. There is no paid tier today. A Pro plan is planned for when the product integrates features that require infrastructure (saved history, team access), but no payment processor is wired and no legal entity has been registered. Until those are in place, the product remains free for everyone.

Previewcard fetches the raw HTML of the page and reads the meta tags from the server-rendered source. It does not execute JavaScript. If your social tags are injected into the DOM by a client-side framework after page load, they are not visible to the HTTP response and will not appear in the report.

To make your tags discoverable, they need to be present in the server-rendered HTML. Static site generators, server-side rendering (SSR), or build-time plugin injection are the standard fixes.