Prerender services not recognizing Tumblr

The most likely culprit: your prerender service doesn’t recognize Tumblr’s user agent (Tumblr/{version}) and serves the JS-only page. Tumblr’s crawler doesn’t run JavaScript, so it sees no OG tags and generates no preview.

This is a Tumblr-specific problem because Tumblr’s user agent has historically been inconsistent, and many prerender service default bot lists don’t include it.

Diagnosis checklist

1. curl your URL with the Tumblr user agent and check for meta tags in the response
2. If you use Prerender.io or similar, confirm Tumblr is in the recognized bot user agent list
3. Verify og:title and og:image are in the HTML
4. Check robots.txt – make sure Tumblr’s crawler isn’t blocked
5. Confirm the page returns 200 OK
6. Double-check the URL you’re pasting into the link post

Prerender service fix

Add Tumblr to your bot user agent whitelist:

Tumblr

This is all most prerender services need to start serving static HTML to Tumblr’s crawler.

Testing your fix

curl -A "Tumblr/1.0" https://yoursite.com/page | grep -i "og:title"

If the tag shows up, create a new link post on Tumblr to confirm the preview renders.