Developer Tool

Regex Validator

Test JavaScript regular expressions against sample text, inspect live matches, review capture groups, and preview replacement output. Free, private, and built for fast debugging.

Runs in browserLive match previewFree & no signup

Regex pattern

Pattern

//gi

Flags

Test text

Sample input

Validation result

Valid regex

Matches

Highlighted text

Contact [email protected] for product questions. For billing, email [email protected] or [email protected]. Invalid examples: support@, @example.com, and plain text.

Matches and groups

Match 1index 8

[email protected]

Match 2index 72

[email protected]

Match 3index 95

[email protected]

Replace preview

Replacement

Contact [email hidden] for product questions.
For billing, email [email hidden] or [email hidden].
Invalid examples: support@, @example.com, and plain text.

How to validate a regex online

Use Regex Validator to test a regular expression against real text before you paste it into your app, script, or editor.

01
Enter your regex pattern
Paste the regular expression without the surrounding slashes. The tool validates JavaScript regex syntax as you edit.
02
Choose regex flags
Toggle global, ignore case, multiline, dot all, Unicode, or sticky flags to match the behavior you need.
03
Add sample text
Paste the text you want to test. Matching sections are highlighted and each match shows its index.
04
Review groups and replacement
Inspect capture groups, copy match data, and preview replacement output before using the regex in your code.

What people use it for

A regex tester helps you confirm pattern behavior before it touches production data or a large batch of text.

Form validation

Test patterns for emails, phone numbers, usernames, product codes, and other user input before shipping them.

Log parsing

Build expressions that extract timestamps, IDs, status codes, and error messages from application logs.

Search and replace

Preview replacement output before running a bulk edit in code, content, CSV exports, or configuration files.

Capture group debugging

Check whether each group captures the intended substring and quickly spot optional groups that do not match.

API and data cleanup

Validate patterns used to normalize imported text, detect malformed values, or extract structured fields.

Learning regex

Experiment with flags, character classes, anchors, and groups using immediate visual feedback.

Frequently asked questions

Yes. Regex Validator is free to use with no signup, no usage limits, and no watermarks.

No. Pattern validation and matching run locally in your browser, so your regex and sample text are not uploaded.

It uses JavaScript regular expressions, the same RegExp engine available in modern browsers.

The tool supports common JavaScript flags: global, ignore case, multiline, dot all, Unicode, and sticky.

Yes. Each match shows numbered capture groups so you can confirm exactly what each group captured.

Yes. Add replacement text to preview the output before using the regex in code or a bulk edit.

Different languages use different regex features. This tool validates JavaScript regex, so language-specific features from PCRE, Python, or .NET may not work.

Yes, but performance depends on your device and pattern complexity. Complex expressions on huge text can be slow in any browser.

Yes. The validator works on mobile browsers, though writing and debugging regex is usually easier on a larger screen.

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How to validate a regex online

Use Regex Validator to test a regular expression against real text before you paste it into your app, script, or editor.

Enter your regex pattern

Paste the regular expression without the surrounding slashes. The tool validates JavaScript regex syntax as you edit.

Choose regex flags

Toggle global, ignore case, multiline, dot all, Unicode, or sticky flags to match the behavior you need.

Add sample text

Paste the text you want to test. Matching sections are highlighted and each match shows its index.

Review groups and replacement

Inspect capture groups, copy match data, and preview replacement output before using the regex in your code.