The Facebook Sharing Debugger is Meta's tool for previewing how a link will look when it's shared to Facebook and for finding problems with its Open Graph tags. Running a URL through it also refreshes what Facebook has scraped from your page, so it's how you update a stale link preview without waiting for Facebook's standard 24-hour update period.
As of October 2026, Meta for Developers says you need to log into Facebook to use it. It shows which meta tags the crawler scrapes, plus any errors or warnings.
Here's the rule that trips up most site owners. Meta's Images in Link Shares page (updated 30 Jun 2026) says Facebook caches every image by its URL. Replace an image but keep the same file URL, and the image won't update. Use a new URL for the new image, and don't delete the old one, because existing shares may still point to it.
Even then, old shares don't change on their own. Meta says updating the image for a URL won't automatically update the preview on posts that were already shared; you have to refresh the share.
How Facebook builds a link preview
When a link is shared for the first time, Meta for Developers says the Facebook crawler scrapes and caches the metadata from that URL. The crawler has to see an image at least once before it can render it, which means the first person to share a fresh page won't see a rendered image.
Without Open Graph tags, the crawler uses its own heuristics to make a best guess at the title, description and preview image. Meta's A Guide to Sharing for Webmasters (updated 30 Jun 2026) says to set these yourself with Open Graph tags to get the highest quality posts on Facebook, because most content is shared as a URL.
The Open Graph tags that control it
| Tag | What Meta for Developers says it's for |
|---|---|
| og:url | The canonical URL for the page, without session variables, user-identifying parameters or counters. Likes and Shares gather at this URL |
| og:title | The title of your article, without branding such as your site name |
| og:description | A brief description, usually 2 to 4 sentences, shown below the title |
| og:image | The URL of the image that appears when someone shares the content |
| fb:app_id | Needed for Facebook Insights, which shows analytics for traffic to your site from Facebook |
| og:type | The type of media, which affects how content shows in Feed. It defaults to website, and each URL takes one value |
| og:locale | The locale of the page. It defaults to en_US |
Meta's tip on og:url is worth following: mobile domain URLs should point to the desktop version as the canonical URL, so Likes and Shares collect in one place across both versions.
Image sizes Meta asks for
| Image rule | Meta for Developers figure |
|---|---|
| Minimum image dimension | 200 x 200 px |
| Maximum file size | 8 MB |
| Recommended for high-resolution screens | At least 1200 x 630 px |
| Minimum for a large link preview | 600 x 315 px |
| Ratio to aim for | About 1.91:1 |
An image smaller than 600 x 315 px still shows, Meta says, just much smaller. The 1.91:1 ratio matters because Meta redesigned link page posts so the image ratio is the same on desktop and mobile Feed. Staying close to it shows the full image without cropping.
Pre-cache new pages so the first share shows an image
Meta lists three ways to make images render on the very first Like or Share:
- Pre-cache with the Sharing Debugger: run the URL through it to pre-fetch the page's metadata. Meta says this also works to update the image for a piece of content.
- Pre-cache with the Graph API: force a scrape of the URL programmatically to pre-fetch the metadata. This can also update the image.
- Add og:image:width and og:image:height tags, so the crawler knows the dimensions and can render the image straight away instead of downloading and processing it first.
For a site that publishes often, the third option is the one that keeps working without anyone having to remember a step.
Fixing a wrong or outdated image
Putting Meta's rules together, this is the order that works when you've changed a page's image:
- Upload the new image at a new URL rather than overwriting the old file.
- Point your og:image tag at the new URL, and don't delete the old image file.
- Run the page URL through the Sharing Debugger so the crawler downloads the new image and refreshes what it holds.
- Refresh any existing shares you want updated, because old shares keep their old preview until you do.
- If an image still won't display, put the image URL itself into the Sharing Debugger to check for errors.
If you think the problem is on Facebook's side, Meta suggests filing a bug report.
Want AI doing the heavy lifting in your marketing?
I build the systems that handle the boring 80 percent, so you get your week back. Done properly, with the human kept in.
When the preview still won't behave
One server setting sits behind a lot of broken previews. Meta for Developers says its crawler only accepts gzip and deflate encodings, and its Sharing best practices page (updated 23 Feb 2022) says you must enable GZIP and/or deflate on your web server for your site to be shared correctly.
Meta also says the debugger triggers a scrape of your page, so once you've fixed errors in your HTML, you can use it to update your content. If the right image appears but looks soft, that's a separate question from caching, and it's covered in whether Facebook compresses photos.
Keep the jobs apart, too. The Sharing Debugger checks previews, not tracking. Measuring what visitors from Facebook do on your site is the job of the Meta Pixel, and the Facebook Pixel Helper checks whether it's firing.
My advice
Treat the Sharing Debugger as the last step of publishing, not just a repair tool. Set og:title, og:description, og:image and og:url on every page, add og:image:width and og:image:height, and keep images at 1200 x 630 px or bigger. Then, whenever you change an image, give it a new file URL and run the page through the debugger. Overwriting an image at the same URL is exactly the mistake Meta's own rules warn about, and it's an easy one to make.
Frequently asked questions
What is the Facebook Sharing Debugger?
A Meta for Developers tool that previews how your content will look when it's shared to Facebook and helps you debug your Open Graph tags. It shows which tags the crawler scrapes and any errors or warnings.
How do I refresh a Facebook link preview?
Run the URL through the Sharing Debugger. Meta says it refreshes any scraped content it holds for your site, which helps when you need changes sooner than the standard 24-hour update period.
Why is Facebook still showing the old image?
Facebook caches images by URL. Meta says to use a new URL for a new image or it won't update, and that posts already shared need refreshing separately.
What size should my og:image be?
Meta recommends at least 1200 x 630 px, with 600 x 315 px as the minimum for larger link previews. The minimum allowed is 200 x 200 px, the file mustn't exceed 8 MB, and about 1.91:1 avoids cropping.
Do I need a Facebook login to use the Sharing Debugger?
Yes. Meta for Developers says you need to log into Facebook to use the tool.
What does the crawler need from my server?
Gzip or deflate encoding. Meta says its crawler only accepts gzip and deflate, so your server needs to use the right encoding.
