Regex Tester

Test and debug regular expressions in real time. Matches are highlighted as you type, with a full match list showing index positions and capture groups. Runs entirely in your browser.

Examples:

Regular expression

//g

Test string

Regex flag reference

/gGlobal

Find all matches instead of stopping after the first.

/iCase-insensitive

Match uppercase and lowercase letters interchangeably.

/mMultiline

Make ^ and $ match the start/end of each line, not just the string.

/sDot all

Allow . to match newline characters (\n).

Using regex with Claude

Claude can write and explain regular expressions. Ask Claude to "write a regex that matches email addresses" or "explain this regex pattern" — then use this tester to verify the result before using it in your code.