Find & Replace

In plain text mode, every occurrence of the search string is treated as a literal substring, so replacing cat also matches inside category unless you build the search term to avoid that. Regular expression mode instead treats the search field as a pattern, letting you match things like any digit, any whitespace run, or an optional character, and use capture groups in the replacement to reuse parts of the match.

This is useful well beyond simple typo fixes: bulk-correcting a misspelled product or company name across a long document, stripping a recurring boilerplate phrase from a pasted transcript, or using a regex pattern to reformat data, such as swapping a date from MM/DD/YYYY to DD-MM-YYYY by capturing each part and rearranging it in the replacement.

A common regex mistake is forgetting that characters like period, parenthesis and asterisk have special meaning in a pattern, so searching for a literal period requires escaping it as a backslash followed by a period rather than typing it plain, and the case-sensitive toggle applies to both plain and regex searches.