AO3 Word Replacer is a free Firefox extension designed to enhance user experience on Archive of Our Own (AO3) by allowing users to replace specific words or phrases with custom alternatives. This tool features options for case-sensitive and whole-word matching, ensuring precision in text modifications. Users can also preserve the original capitalization pattern of the replaced text, making the substitutions seamless and contextually appropriate.

The extension provides a straightforward settings overview where users can define the original word or phrase, specify the replacement, and choose matching preferences. Data is stored locally in the browser, ensuring privacy, and users can easily export or import their replacement lists when switching browsers or devices. Overall, AO3 Word Replacer is a practical tool for enhancing the reading experience on AO3.