Regex find and replace: a practical cheat sheet

Plain find and replace swaps one exact piece of text for another. Regular expressions (regex) let you match patterns instead: any number, any email address, any line that starts with a certain word. Combined with replacement references, they can restructure text in ways that would take hours by hand. This is a practical cheat sheet for the patterns that come up most in everyday text cleanup.

The building blocks

• . matches any single character except a line break.
• \d matches a digit, \w a letter, digit, or underscore, and \s any whitespace, including spaces, tabs, and line breaks.
• [abc] matches any one of the listed characters; [a-z] matches a range; [^abc] matches anything except those characters.
• ^ matches the start of a line and $ the end of a line. (Some tools apply these to the whole text instead unless multiline mode is on; the tool on this site always works line by line.)
• \ escapes a special character, so \. matches a literal period.

Repetition

• * means zero or more, + means one or more, and ? means zero or one.
• {3} means exactly three, and {2,5} means between two and five.
• Adding ? after a repeat makes it lazy, matching as little as possible: ".*?" matches one quoted string rather than everything from the first quote to the last.

Groups and references

Parentheses create a capture group. In the replacement, $1 refers to the first group, $2 to the second, and $& to the whole match. This is what makes regex replace so powerful.

Recipes

1. Swap "Last, First" to "First Last": find (\w+), (\w+) and replace with $2 $1.
2. Collapse repeated spaces: find {2,} (a space followed by a count) and replace with a single space.
3. Remove trailing whitespace: find [ \t]+$ and replace with nothing.
4. Wrap every number in brackets: find \d+ and replace with [$&].
5. Reformat dates from 2026-09-24 to 09/24/2026: find (\d{4})-(\d{2})-(\d{2}) and replace with $2/$3/$1.
6. Convert tabs to commas: find \t and replace with ,.
7. Strip HTML tags from a snippet: find <[^>]+> and replace with nothing. (Fine for quick cleanup, but not a safe way to sanitize untrusted HTML.)
8. Find duplicated words like "the the": find \b(\w+) \1\b and replace with $1.

Common mistakes

• Forgetting to escape special characters. Characters like . * + ? ( ) [ ] { } | ^ $ \ all have special meaning. To match a literal period in "example.com", use example\.com, or turn regex mode off so the text is matched literally.
• Greedy matches that swallow too much. <.*> on a line with two tags matches from the first < to the last >. Use <.*?> or <[^>]*> instead.
• Case sensitivity. Decide whether "Apple" and "apple" should both match, and set the option accordingly.
• Testing on the whole document at once. Try a pattern on a small sample first, and check the match count before trusting the result.

Try it

The find and replace tool supports JavaScript regular expressions with $1 and $& references in regex mode, shows a live match count, and never changes your original text, so you can experiment safely. With regex mode off, both the search and replacement text are treated literally.