FoxReplace is a Firefox extension developed by Marc Ruiz that brings the ability to search and replace text occurrences in a web page.

It adds an intuitive menu item to the Edit. Unfortunately the most common Ctrl + H keyboard shortcut is already in use by the History sidebar, so you will have to settle with Shift + F2.

The replace dialog (displayed at the bottom of the current window) allows you to search whole words, parts or use regular expressions. You then enter what you’re looking for, what you want it replaced with, set case sensitivity, hit the Replace button and all substitutions happen at once which may be a limitation in some situations.

There is no option to search and replace on a text area only which I would really appreciate. It also abuses the Tools menu adding yet another item to set rarely used options.

Substitution rules import and export and automatic replacements are an overkill for me but the options are there anyways.

If you do a lot of editing in the web you will most likely appreciate FoxReplace, available at Mozilla Add-ons.