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My version of Firefox is 3.5.9, but I've had this issue since single-image tabs started showing a thumbnail of the contained image.

Typically, a tab containing a single image will use a thumbnail of the image as the icon before the tab title. Sometimes, though, this icon will be the generic “shaded sphere on blank page” (or perhaps whatever your theme defaults to). I'm guessing this happens whenever height or width is larger than 1024, but I seem to recall (perhaps erroneously) exceptions to this rule. Anyway, hopefully someone will know the definite answer to:

Why does this happen?


Images showing thumbnails

Images not showing thumbnails


I would appreciate even more a link to the source file or even a patch that explains this behaviour, if it's not a bug. I've tried to locate such a code snippet, but I was unsuccessful.

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up vote 2 down vote accepted

It's not a bug, but rather a solution to a bug

To help users differentiate between images loaded in tabs, Firefox sets the tab icon (and the icon in the Location Bar) to a small version of the image. Early tests of this feature revealed performance problems; to address this, Firefox only shows the image’s thumbnail in the tab and Location Bar if the image is smaller than a certain size. This preference determines the cutoff.

Source: wiki page

So if you do an about:config in Firefox's address bar and search for you can chage that value to something larger, but be aware you may suffer some performance hit.

You could also see about fixing the bug. One route to a solution might be to pull out the exif thumbnail (where available) and resize that instead.

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Thank you, your answer was spot-on. – tzot Apr 18 '10 at 0:10

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