Regex Tester
Test a regular expression live — matches highlighted, groups listed
Test string
matches
Regex Tester — Complete Guide & Instructions
MakeCard Regex Tester evaluates a JavaScript regular expression against your test string in real time. Type a pattern, toggle the g, i, m and s flags, and every match is highlighted inline while a numbered list below shows each match, its position, and any capture groups. It is a fast, private sandbox for building and debugging patterns before dropping them into code.
How to Use Regex Tester
- 1 Type your pattern into the Pattern field (e.g. \b\w+@\w+\.\w+).
- 2 Toggle the flags you need — g (global), i (case-insensitive), m (multiline), s (dot-all).
- 3 Paste your test string into the Test string area.
- 4 See matches highlighted in the preview and listed with index and capture groups.
- 5 Refine the pattern — matches update live as you type.
Key Features & Capabilities
- Live matching — results update on every keystroke.
- Inline highlighting of every match in the test text.
- Numbered match list with text, index and capture groups.
- Flag toggles: g (global), i (ignore case), m (multiline), s (dot-all).
- Clear error display for invalid patterns.
- Everything runs locally — patterns and text stay on your device.
Supported Formats & Specifications
| Parameter | Specification |
|---|---|
| Engine | JavaScript RegExp (the same engine your web code uses) |
| Flags | g · i · m · s |
| Match Details | Matched text, index, and capture-group values |
| Match Cap | First 500 matches displayed |
| Processing | Client-side, real-time |
Practical Everyday Use Cases
- Building a validation regex for email, phone or custom inputs.
- Debugging why a pattern matches too much or too little.
- Verifying capture groups extract the right substrings.
- Testing multiline and dot-all behavior before shipping code.
- Learning regex interactively with instant feedback.
Pro Tips for Best Results
- Start with the g flag on — without it you only see the first match.
- Remember \b for word boundaries — it stops partial matches inside longer strings.
- Check the index values to confirm matches land where you expect.
- The engine is JavaScript's — syntax for lookbehind, named groups, etc. follows JS rules, not PCRE.
Common Problems & Solutions
Check escaping — backslashes need a single \ here (unlike code strings). Also try the i flag if case is the issue.
Turn on the g (global) flag — it is required to see every match.
The syntax is off — look for unbalanced (), [], or an illegal escape; the message points to the problem.
Privacy & Security
100% Client-Side Execution
Patterns and test text are evaluated entirely in your browser — nothing is sent to a server.
Frequently Asked Questions
Everything you need to know about using Regex Tester
Type the pattern and paste your test string — matches are highlighted live with positions and capture groups listed below.
g finds all matches, i ignores case, m makes ^ and $ match line starts/ends, and s lets the dot match newlines.
JavaScript's RegExp engine — patterns behave exactly as they would in web code.
They appear in the match list under each numbered match as groups: [...].
In code, backslashes inside string literals need doubling (\d → "\\d"); here you write the raw pattern.
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