How this works in your browser
Replacement uses the browser's own regular expression engine, which is why enabling regex gives you the full JavaScript syntax rather than a limited subset: capture groups, character classes, quantifiers, anchors and word boundaries all work as they would in code. In plain mode the search term is treated literally, matching anywhere in the text including inside longer words, which is the behaviour that produces most unexpected results. Invalid patterns are caught and reported rather than silently failing, since a malformed regex would otherwise throw and appear as the tool doing nothing. Everything runs locally with no transmission.
Who uses Find and Replace Tool
Cleaning up pasted text
Strip repeated artefacts left over from another application.
Bulk renaming and updating
Change a term consistently across a long document.
Reformatting data
Use regex with capture groups to restructure lines rather than just substitute.
Redacting before sharing
Replace names or identifiers throughout a document locally.
Frequently asked questions
Can I use regular expressions?
Yes - enable "Treat find as regex" to use full JavaScript regular expression syntax in the find field.
Does it replace all matches or just the first?
All matches are replaced by default.
What happens with an invalid regex?
The tool shows a clear error message explaining the pattern is invalid, rather than crashing.
Why did my replacement hit words I did not intend?
Because a plain find matches anywhere, including inside longer words. Replacing 'cat' also changes 'category' and 'concatenate'. Enabling regex and wrapping the term in word boundaries restricts it to the whole word, which is the fix for by far the most common surprise here.
What regex patterns are actually worth knowing?
Four cover most real work: a dot for any character, an asterisk or plus for repetition, square brackets for a set of characters, and word boundaries to match whole words. Groups captured in parentheses can be referenced in the replacement, which is how you reorder or restructure text rather than just substitute it.
Can I undo a replacement?
Not within the tool, since it produces new output rather than editing in place. Your original is still in the input field, so the practical safeguard is to check the result before copying it out, and to keep a copy of anything important before making a sweeping change.
Is my text uploaded anywhere?
No. The replacement runs in your browser, so you can safely clean up documents containing names, addresses or internal information.