Regex Tester

Regex Tester lets you write a pattern and immediately see which parts of your sample text it matches, with each match highlighted in a distinct color. Toggle the standard flags — global (g), case-insensitive (i), multiline (m), dot-all (s), sticky (y), and unicode (u) — and the match set updates as you flip each switch. The tool draws on JavaScript's native RegExp engine, so results match what your code will actually do at runtime. That matters because regex flavors differ across languages: a pattern that works in Python's re module or Java's java.util.regex may behave differently in a browser. Testing here removes that guesswork before you ship. Practical scenarios show up everywhere: validating email addresses and phone numbers in form inputs, extracting all URLs from a block of HTML, parsing log lines into structured fields, stripping markdown formatting, finding duplicate words in a document, or splitting a CSV-like string on delimiters that may or may not be quoted. Capture groups are displayed individually, so you can confirm that your parentheses grabbed exactly the substring you expected. Each match shows its index position, the full matched text, and the contents of every capture group. Invalid patterns produce a clear syntax error pointing to the problematic token, rather than failing silently.