I would assume that this button comes with an installed and enabled extension.

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox has some built-in features to take a full page screenshot. Firefox Screenshots extension that stores a screenshot online.

• https://pageshot.net/

A built-in Web Developer feature.

• https://developer.mozilla.org/en/Tools/Taking_screenshots

Why don't people answer the question? Firefox has a Toolbars and Features menu, with an image of a camera on it, with the text "Capture Page Thumbnail" under it. It's not something I downloaded; it came with Firefox. When you click this icon, a camera sound "click" audio file is heard. But there are no images of the "captured page thumbnail" to be found. Not in the "download" folder. Not in any Firefox folders. Not in the Pictures sections of windows 10. Please, can whoever it is working with Mozilla Firefox that put that icon and click sound file in Firefox please inform us, the public who use Firefox, what it is, what it does, and if there is a thumbnail being created, where the thumbnail / image is? Please?

If you click the Download button (down pointing arrow) then the image is saved in the folder set as the default download location in "Options/Preferences -> General" whether this choice is selected or "always ask" is selected. You can temporarily select the 'Save files to' setting to modify the default location and then select 'always ask' again.

Thanks but this did not work. After designating a new download folder and using the "Capture Page Thumbnail" tool, no new files were created; neither in the designated directory, nor shown in the Quick Access area where new & recent files are recorded.

Like most applications, FireFox maintains a folder/directory for temporary items like images etc.

On Windows, the thumbnails produced by the 'take screenshot' function are cached at:-

C:\<NameOfUser>\AppData\Local\Mozilla\Firefox\Profiles\Default\thumbnails

...assuming the user profile is on the C:\ drive of course.

There is likely a corresponding folder for Linux etc but we can't say which one this is. Hopefully this response will provide enough info to point toward it.

Hope this helps.

Thumbnails stored in this thumbnail folder in AppData\Local are images that are used for the tiles on the about:newtab page and have nothing to do with the screenshot extension that you can use to take a screenshot of a web page.

cor-el said

Thumbnails stored in this thumbnail folder in AppData\Local are images that are used for the tiles on the about:newtab page...

True - about:newtab thumbnails are stored here.

cor-el said

...have nothing to do with the screenshot extension that you can use to take a screenshot of a web page.

Not true. Clicking "Capture Page Thumbnail" definitely puts a copy of the current page into this folder - regardless of whether the page has been visited beforehand or thumbnailed already for about:newtab.

Having said that, it doesn't follow that this behaviour will be true if using one of the aforementioned extensions, which are in fact unrelated to the original question.

This outcome has been tested and confirmed repeatedly on the following platform:- Windows 7 Firefox 54.0.1 (64-bit)

This 'take screenshot' action might trigger Firefox to store a new thumbnail, but the real screenshot image should be in the default downloads folder.