Set up Thumbnail: forums, image sources and rebuilding

Thumbnail adds a small image to each thread in your thread lists, widgets and search results, picked automatically from the thread's first post. Right after install it shows nothing, because it only works in forums you choose, and no forum is chosen at first. Pick the forums, decide where images may come from, and fill in thumbnails for the threads you already have. It needs XenForo 2.3.

Choose the forums

Go to Setup > Options > D.C Style - Thumbnail. The first option, Forums limit, lists your forums. Select All at the top, or hold Ctrl (Cmd on a Mac) and click each forum you want. Until you do, no thread gets a thumbnail.

Decide where images come from

For each thread, Thumbnail looks at the first post and takes the first image it can use. The options control which sources count:

• Attachments in the first post are always used.
• Enable external images? uses images posted with [IMG] from other sites.
• Enable media thumbnail images uses the preview image of embedded YouTube, Vimeo and Dailymotion videos.
• Poster BBCode tags uses posters from your own custom BB codes, for example TMDB,IMDB. If a tag shows no image, the optional TMDB API read token looks the title up on TMDB instead.
• When a thread has no image at all, Use user avatar for default thumbnail shows the author's avatar or Gravatar. Otherwise the Default thumbnail image is used.

Note: If you use a TMDB token, TMDB's terms require you to show their logo and the notice "This product uses the TMDB API but is not endorsed or certified by TMDB" in an About or Credits section of your forum.

Video previews are fetched from YouTube, Vimeo and Dailymotion by your server, which needs PHP's allow_url_fopen enabled. If your host has turned it off, video threads get no thumbnail while attachments and images still work. Optimize images locally decides which of those images are downloaded, resized and stored on your server. That makes pages lighter, and it is on for external images by default.

Sizes and appearance

The thumbnail is 36 by 36 pixels by default, with separate width and height settings for thread lists and for widgets, plus a Thumbnail border radius (4 pixels). Thumbnail on search results shows them in search too. Thread pages also use the thumbnail as the image shown when a thread is shared on social media.

Fill in thumbnails for existing threads

New and edited threads get their thumbnail automatically, as long as Auto rebuild thumbnail cache after first post changes is on (it is by default). For threads posted before you installed, run a rebuild:

1. Go to Tools > Rebuild caches.
2. Find Rebuild thread thumbnails and run it. Tick Rebuild threads already have thumbnail only if you want existing thumbnails worked out again, which takes longer.
3. If you set up poster BB codes, also run Fill missing posters from configured BBCode tags.

On a large forum, the command line has no browser time limit:

php cmd.php xf-rebuild:dcThumbnail-thumbnail

Running XenForo commands over SSH explains the basics.

Let members choose their own thumbnail

Two permissions in the D.C Style - Thumbnail section of Groups & permissions > User group permissions control this. Can edit own thread thumbnail lets members upload an image, pick one from the post or choose none for their own threads. Can edit any thread thumbnail is for moderators. XenForo permissions explained.

If thumbnails do not appear

• Check Forums limit first. It is the cause most of the time.
• Generated images are saved in your forum's data folder, so the web server must be able to write to it.
• Custom styles that change the thread list can stop Thumbnail's template changes from applying. Template modification errors shows how to check.

Thumbnail is also what the image layouts in D.C Style Widgets use. More on the Thumbnail page.

Still stuck? Open a support ticket with your XenForo version, a link to a thread without a thumbnail, and what its first post contains.