Regex Tester
Test regular expressions with flags and inspect all matches with capture groups.
Enter a pattern and text.
What is Regex Tester?
Regex Tester lets you write and test regular expressions against any text in real time. It shows all match positions and capture groups so you can debug patterns quickly without running code.
How to use
- Enter your regex pattern in the Pattern field (without leading/trailing slashes).
- Optionally add flags in the Flags field. Common flags:
g(global),i(case-insensitive),m(multiline). - Paste the text you want to test in the Test Text area.
- Matches and their character positions appear in the result area immediately.
Notes
- Uses JavaScript's built-in
RegExp. Syntax follows the ECMAScript standard. - Without the
gflag, only the first match is returned. - Backslashes in the pattern field do not need to be doubled (e.g., use
\d, not\\d).
FAQ
- What regex flavor does this use?
- JavaScript ECMAScript regex. This is compatible with most modern languages for basic patterns, but advanced features like lookbehind with variable length may differ from PCRE (Python, PHP).
- How do I match a literal dot?
- Escape it with a backslash:
\.. An unescaped dot matches any character except a newline. - What are capture groups?
- Parentheses create capture groups, e.g.
(\w+)@(\w+). The result shows extracted group values alongside the full match.
Overview
Test regular expressions with sample text and flags. Useful for validation rules, log parsing, and extraction checks.
How to use
- Enter pattern and test text.
- Set flags such as g/i/m.
- Run and inspect matches and groups.
Examples
-
Email-like match
Input: Pattern: \w+@\w+\.\w+
Output: Finds simple email-like strings.
-
Line start
Input: Pattern: ^ERROR (m flag)
Output: Matches ERROR at each line start.
Notes
- Some engines differ in regex syntax.
- Overly broad patterns can cause slow performance.
- Escape backslashes correctly.
FAQ
- Why no match found?
- Check anchors, flags, and escaping first.
- What does g flag do?
- It searches all matches, not just the first.
- Can regex freeze input?
- Complex backtracking patterns can be expensive.
Embed this tool
Paste this iframe into any HTML page to embed Regex Tester on your site:
Related Tools
-
UUID Generator
Generate random UUID v4 identifiers for apps, APIs, and databases.
-
Unix Timestamp Converter
Convert Unix timestamps to readable dates and dates back to Unix time.
-
JSON Formatter & Validator
Format and validate JSON with readable indentation and clear parse errors.
-
HTML Entity Encoder / Decoder
Encode special HTML characters into entities or decode entities back to text.
-
Hash Generator (SHA-256 / SHA-1)
Generate common text hashes including SHA-256 and SHA-1.