Overview
facebookexternalhit is Facebook's web crawler that fetches metadata and images whenever someone shares a URL on Facebook, Messenger, or Instagram. It reads the Open Graph meta tags from your page to build the link preview card — the image, title, and description that appear in the post.
Facebook created the Open Graph protocol in 2010, so their crawler is arguably the most important bot to optimize for when it comes to OG images. Every major platform adopted the same protocol, making facebookexternalhit the de facto standard-setter for link preview behavior.
The crawler runs from Facebook's IP ranges and follows redirects. It makes a GET request to your URL, parses the HTML for OG meta tags, and fetches the og:image URL separately. If your OG image URL also redirects, it will follow those too — up to a reasonable limit.
User-Agent Strings
Facebook Crawler identifies itself with the following user-agent strings:
facebookexternalhit/1.1 (+https://www.facebook.com/externalhit_uatext.php)facebookexternalhit/1.1facebookcatalog/1.0How Facebook Crawler Handles OG Images
Facebook's crawler reads the full suite of Open Graph tags since they invented the protocol. It is the most thorough OG consumer.
Meta Tags Read
og:imageog:image:widthog:image:heightog:image:typeog:titleog:descriptionog:urlog:typeog:site_name| Preferred Size | 1200 × 630 |
| Minimum Size | 200 × 200 |
| Max File Size | 8 MB |
| Cache Duration | 24+ hours |
Caching Behavior
Very aggressive. Facebook caches OG data for at least 24 hours, often longer. The only reliable way to refresh the cache is to use the Sharing Debugger tool and click "Scrape Again". Appending a query parameter to the URL forces a fresh fetch.
Fallback Behavior
If no og:image tag is found, Facebook's crawler will attempt to use the first sufficiently large image on the page (at least 200 × 200 pixels). If no suitable image is found, the link preview appears as text-only.
Things to Know
- If you omit og:image:width and og:image:height, the crawler makes an additional HEAD request to determine image dimensions — this can slow down preview generation.
- Images smaller than 200 × 200 pixels are ignored entirely.
- The crawler runs from a limited set of IP ranges. If your server is behind a firewall or CDN, make sure these IPs are allowed.
- Facebook prefers og:image URLs with a file extension (.png, .jpg). URLs without extensions work but may be processed slower.
robots.txt
Respects robots.txt under normal circumstances. Facebook may bypass robots.txt only for security or integrity checks (e.g., malware scanning). The directive controls general crawling behavior.
User-agent: facebookexternalhit
Allow: /How to Test
Facebook provides the Sharing Debugger, the most comprehensive tool for testing how your OG tags are parsed. It shows exactly which tags were found, the resolved image, and any warnings about missing or malformed tags.
- Click "Scrape Again" to force a fresh fetch — useful when you've updated your OG tags.
- Check the "Warnings" section for issues like missing og:image:width/height tags.
- The debugger shows the raw values it found, so you can verify your tags are being read correctly.
You can also use the MyOG OG Preview tool to check how your OG tags are configured before testing with Facebook Crawler.
FAQ
What is facebookexternalhit?
facebookexternalhit is Facebook's web crawler (also called a bot) that fetches metadata from web pages when URLs are shared on Facebook, Messenger, or Instagram. It reads Open Graph meta tags to generate link preview cards with an image, title, and description.
Why isn't Facebook showing my OG image?
Common causes: your image is smaller than 200 × 200 pixels, the og:image URL returns an error or redirect loop, your server blocks Facebook's crawler IPs, or Facebook has cached an older version. Use the Sharing Debugger and click "Scrape Again" to force a refresh.
How do I clear Facebook's OG image cache?
Visit the Facebook Sharing Debugger at developers.facebook.com/tools/debug/, enter your URL, and click "Scrape Again". This forces Facebook to re-fetch your OG tags. For stubborn caches, add a query parameter like ?v=2 to your URL to force a completely fresh fetch.
Related Bots
Test Your OG Images
Check how your Open Graph images appear to bots and crawlers. Preview your link cards before sharing.
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