An Open Graph image is the picture shown when a link to your page is pasted into a chat app, a social feed or a messaging tool. The wrong size does not usually break the preview outright, but it does mean the image gets cropped, letterboxed or stretched in ways you did not choose, since every consuming platform lays the image into a fixed aspect ratio container rather than adapting its container to your image.
The check runs entirely in your browser using the image's own decoded dimensions. Nothing is uploaded, which matters for checking an image tied to a page that has not gone live yet.
Why a 1200x630 og image became the open graph image dimensions standard
1200 by 630 pixels produces a 1.91 to 1 aspect ratio, which is the ratio Facebook's own documentation has recommended for years and which most other platforms that render link previews, including many messaging apps and some social networks, have converged on as a practical default. At that resolution the image also stays comfortably above the minimum size several platforms enforce before they will even attempt to show a large image preview at all.
Following this size does not guarantee identical rendering everywhere, since some surfaces crop to a perfect square and others use a shorter wide banner, but 1200 by 630 sits close enough to most of those variants that a straight crop rarely cuts off anything important, which is the real practical reason it has become the default target rather than any single platform's absolute requirement.
What actually goes wrong with the wrong aspect ratio
A square image placed into a wide 1.91 to 1 container is not stretched, it is cropped, since virtually every consumer of Open Graph data fits the image into its own fixed container rather than resizing the container to match an arbitrary aspect ratio. Depending on the platform that crop takes either the centre of the image or an algorithmically chosen focal point, and text or a logo placed near the top or bottom edge of a square source image is a common casualty.
A very wide banner image suffers the opposite problem: cropped down to a shorter container, its edges are trimmed and content placed near the left or right border can be lost entirely. Designing the source image with generous, empty margin around anything essential is the practical defence against both failure modes.
How this og image size checker reads the real dimensions
The loaded file is decoded by the browser's native image handling, and the check reads the resulting element's naturalWidth and naturalHeight properties, which reflect the image's true pixel dimensions as decoded, independent of any CSS sizing or how large the file happens to display on a page. This is the same information a browser itself relies on internally and is not affected by a misleading file name or an incorrect assumption based on file size in kilobytes.
Reading natural dimensions this way also catches a common mistake: an image saved at the correct aspect ratio but the wrong absolute resolution, for example 600 by 315, which is proportionally identical to 1200 by 630 but is likely below the minimum several platforms require before they render an image at full preview size rather than a small thumbnail.
Facebook link preview image size versus other platforms
Facebook's own guidance is the origin of the 1200 by 630 recommendation, but the facebook link preview image size target has effectively become the de facto standard other platforms measure themselves against too, including link unfurling in many chat apps. A dedicated Twitter or X card image follows its own summary_large_image convention, close to but not identical to Open Graph's ratio, which is why a site aiming for pixel perfect results on every platform sometimes maintains a second, purpose built card image rather than relying on one shared og:image for everything.
For most sites, one well chosen 1200 by 630 image handles every major platform acceptably well, and maintaining a second image is only worth the extra effort once a brand's visual presentation on social platforms is a genuine priority rather than an afterthought.
Minimum size and file weight limits worth knowing
Beyond the aspect ratio, most platforms also enforce a minimum absolute size, commonly around 200 by 200 pixels, below which a large image preview is not offered at all and a small thumbnail or no image is shown instead. Several platforms additionally cap the file size of the image itself, commonly somewhere in the single digit megabytes, which is rarely a concern for a normally compressed JPEG or WebP but can catch an uncompressed PNG export.
Checking pixel dimensions, as this tool does, and separately checking file size and format compatibility covers the two most common reasons an otherwise well designed Open Graph image fails to render as intended.
How to check an OG image size
- 1
Load your image
Choose or drop the image file you plan to use as og:image.
- 2
Read the natural dimensions
See the exact decoded pixel width and height, independent of the file's display size.
- 3
Compare the aspect ratio
Check the calculated ratio against the 1.91 to 1 ratio behind the 1200x630 recommendation.
- 4
Resize if flagged
If the check fails, resize or recrop the image to 1200 by 630 pixels before publishing it.
Related tools worth bookmarking
Sources and further reading
Frequently asked questions
Common questions about the og image size checker.
1200 by 630 pixels produces a 1.91 to 1 aspect ratio, which Facebook's documentation has recommended for years and which most other platforms rendering link previews have converged on as a practical default. It sits close enough to the variants different platforms actually use that a straight crop rarely cuts off anything important.
No. The image is loaded and decoded entirely in your browser, and its natural width and height are read directly from the decoded element. Nothing is transmitted to a server, which is useful for checking an image tied to a page that has not been published yet.
It can be. Several platforms enforce a minimum absolute pixel size, commonly around 200 by 200 pixels, below which a large preview image is not shown at all regardless of aspect ratio. An image proportionally correct but very small, such as 600 by 315, may still render as a small thumbnail rather than a full sized preview.
Not necessarily. A dedicated card image follows a summary_large_image convention that is close to but not identical to the Open Graph ratio. For most sites, one well chosen 1200 by 630 image works acceptably well across every major platform, and a second purpose built image is only worth the extra effort once social presentation is a genuine design priority.
It is not stretched. Almost every platform crops the image into its own fixed container instead, which means a square image loses its top and bottom in a wide container, and a wide banner loses its left and right edges in a narrower one. Keeping essential content, logos and text away from the edges protects against both outcomes.