If you regularly have to work with multiple checkboxes on a page then you might feel a bit frustrated at performing the same operation over and over again. It might be fun to check one or two boxes from time to time but what about ten on each page on twenty pages per day? That’s hard boring work and many users would give a lot to ease that feeling of boredom and repetitiveness.
Enter Checkfox. A Mozilla Firefox add-on that has been designed for users who work regularly with checkboxes. The add-on basically provides the means to check or uncheck multiple checkboxes at once. This is done by selecting the area of the page containing the checkboxes and right-clicking afterwards.
The right-click context menu will display options to check or to uncheck the checkboxes in the selected area. It will only display options to check or to uncheck the boxes if all are unchecked or checked.

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I had a similar problem once, but I needed to check all – and I solved it by writing a new filter for my software http proxy, that made all checkboxes on certain pages checked, changing HTML code on-the-fly.
One more filter added second action on checkboxes button on the top of the page without bothering the web-designer :)