Regex Tester

A regular expression (regex) is a sequence of characters that defines a search pattern. It is used to match, find, and manipulate text. For example, the pattern \d+ matches one or more digits. Regex is supported in virtually every programming language including JavaScript, Python, Java, and PHP. The Dewx Regex Tester lets you build and test patterns interactively with real-time highlighting.

Regex flags modify how the pattern is matched. The most common flags are: g (global) to find all matches instead of stopping at the first, i (case insensitive) to ignore upper/lowercase differences, m (multiline) to make ^ and $ match start/end of each line, s (dotall) to make the dot match newline characters, and u (unicode) for full Unicode support. You can combine multiple flags in the Dewx Regex Tester by clicking the flag buttons.

Capture groups are portions of a regex pattern enclosed in parentheses (). They let you extract specific parts of a match. For example, in the pattern (\d{4})-(\d{2})-(\d{2}) matching "2026-02-07", group $1 is "2026", $2 is "02", and $3 is "07". Named groups use the syntax (?<name>...) and can be referenced by name. The Dewx Regex Tester displays all capture groups for every match.

Regex replace lets you find text matching a pattern and substitute it with a replacement string. In the replacement, you can reference capture groups using $1, $2, etc. for numbered groups, or $<name> for named groups. For example, replacing (\w+)@(\w+) with "$1 at $2" would turn "user@domain" into "user at domain". Toggle Replace mode in the Dewx Regex Tester to preview replacements in real-time.

The Dewx Regex Tester provides real-time match highlighting with colored backgrounds, a detailed match results panel with capture groups, a built-in library of common regex patterns (email, URL, phone, IP, date, and more), and a live replace mode with preview, all in a clean, ad-free interface. Plus, Dewx is building an all-in-one business operating system with unified inbox, CRM, AI automation, and more. Join the beta to streamline your workflow.