Last updated 28 August 2026
Three levels of precision
Plain text replacement is the blunt instrument, and it catches more than people expect — searching for "cat" will happily rewrite the middle of "concatenate". Whole-word matching fixes that by requiring a word boundary at each end, which is usually what you meant. Regular expressions are the precise option: they let you match patterns rather than fixed strings, and capture groups let parts of the match be carried into the replacement. That power comes with a sharp edge, so a malformed pattern is reported here rather than silently doing nothing. Everything updates live as you type, and the match count tells you whether the pattern is doing what you think before you copy anything out.
Common questions
What does whole words only actually match?
It requires a word boundary on both sides of the match, so “cat” matches the word cat but not the middle of “concatenate”. Boundaries fall between letters or digits and anything else, including punctuation and spaces.
How do capture groups work in the replacement?
With regular expression mode on, brackets in the pattern create numbered groups, and $1, $2 and so on insert them into the replacement. Searching for (\\w+)@(\\w+) and replacing with $2 keeps only what followed the at sign.
What happens if my regular expression is invalid?
The error is shown and the original text is left untouched. Nothing is replaced until the pattern is valid, so a half-typed expression cannot damage your text.
Is my text uploaded anywhere?
No. The replacement runs in your browser and nothing is sent to a server.