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Regex Tester Online - Test JavaScript Regular Expressions

Test regex patterns online with live matches, highlighting, capture groups, flags, and syntax errors. Runs locally in your browser.

Browser-based

Use it instantly with no installation.

Local processing

Your input stays in your browser.

No sign-up

Open the tool and get results.

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Regular Expression

/ /

Flags

Test String

Highlighted Matches

0 matches

Match Details

Continue Workflow

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Example

Find email addresses in text

This simple pattern is useful for learning, but production email validation usually needs stricter rules.

Input


                        Pattern: [a-z]+@[a-z]+\.[a-z]+
Flags: gi
Text: Contact hello@quicktoolflow.com or support@example.org

Output


                        Matches: hello@quicktoolflow.com, support@example.org

Practical Notes

Use the g flag when you want to find every match instead of only the first match.
Parentheses create capture groups. The match details section shows what each group captured.
If the regex is invalid, the browser will show a syntax error before matching starts.

How to Use

1. Enter a regular expression pattern without the surrounding slashes.
2. Add flags such as g for global matching or i for case-insensitive matching.
3. Paste sample text into the test string field.
4. Review highlighted matches, match indexes, and capture group details.

Features

Tests JavaScript regular expressions in real time
Highlights every match in the sample text
Shows match positions and captured groups
Supports common flags such as g, i, m, s, u, and y
Displays syntax errors as you type
Runs locally without sending your test text to a server

Use Cases

Debugging validation patterns for emails, slugs, IDs, and log lines
Checking capture groups before using a regex in code
Learning how flags change matching behavior
Testing extraction patterns against realistic sample text

Frequently Asked Questions

Which regex flavor does this tester use?

It uses JavaScript regular expressions through the browser RegExp engine. Some patterns from PCRE, Python, or .NET may behave differently.

What does the g flag do?

The g flag enables global matching, so the tester finds all matches instead of stopping after the first one.

Why are my capture groups empty?

A capture group can be empty if that optional part of the pattern did not match. Check optional groups, alternation, and greedy quantifiers.

Is my sample text uploaded?

No. The regex is compiled and tested locally in your browser, so sample text is not uploaded to QuickToolFlow.

Can I use this regex tester for JavaScript patterns?

Yes. This tool uses the browser JavaScript RegExp engine, which makes it useful for testing patterns before using them in frontend code, Node.js scripts, or browser validation.