What regex flavor is used?

This uses JavaScript's native RegExp engine, the same one used in browsers and Node.js.

Can I see capture groups?

Yes, each match's capture groups are listed alongside the full match text.

Is my test text sent anywhere?

No, all matching happens instantly and locally in your browser.

Can I test regex flags like global or case-insensitive?

Yes. Toggle g, i, m, s, u, y and d. Without g only the first match is found, and the status bar reminds you.

Does it support named capture groups?

Yes. Named groups are listed by name, with the start and end position of each group when the d flag is on.

Why does my regex work here but not in another language?

This tool uses JavaScript's regex engine. PCRE, Python and others differ in syntax such as lookbehind support, possessive quantifiers and named group syntax, so check your language's flavour.

Can I test replacement strings, not just matches?

Yes. Open the Replace tab, enter a replacement such as $2-$1 or $ , and see the result live. The Split tab shows how the pattern splits the text.

What happens if my pattern takes too long?

The pattern runs in a background worker. If it takes over 1.5 seconds (usually catastrophic backtracking from nested quantifiers such as (a+)+), it is stopped and you get a clear message instead of a frozen tab.

Processed 100% locally in your browser

Regex Tester

Test regular expressions with live highlighting, groups, replace and split, a pattern explainer and a library of common patterns — 100% local.

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Quick Answer

Regex Tester lets you: Test regular expressions with live highlighting, groups, replace and split, a pattern explainer and a library of common patterns — 100% local. To start, type it between the slashes, or load one from Common patterns.

How to use this tool

1
Enter your pattern
Type it between the slashes, or load one from Common patterns.
2
Set flags
Toggle g, i, m, s, u, y and d — the Global flag really controls whether every match is found.
3
Add test text
Matches are highlighted in the editor as you type; capture groups are shown in a second colour.
4
Explore the result
Use Matches, Replace, Split, Explain and Cheat sheet to inspect groups, preview a replacement, split text or read what each part of the pattern does.

Frequently Asked Questions

JSON Formatter

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CSV to JSON

Convert CSV to JSON and back, with delimiter detection, type detection and a table preview — 100% local.

Regex Tester

How to use this tool

Enter your pattern

Set flags

Add test text

Explore the result

Frequently Asked Questions

What regex flavor is used?

Can I see capture groups?

Is my test text sent anywhere?

Can I test regex flags like global or case-insensitive?

Does it support named capture groups?

Why does my regex work here but not in another language?

Can I test replacement strings, not just matches?

What happens if my pattern takes too long?

Related Tools

JSON Formatter

CSV to JSON

Regex Tester

How to use this tool

Enter your pattern

Set flags

Add test text

Explore the result

Frequently Asked Questions

What regex flavor is used?

Can I see capture groups?

Is my test text sent anywhere?

Can I test regex flags like global or case-insensitive?

Does it support named capture groups?

Why does my regex work here but not in another language?

Can I test replacement strings, not just matches?

What happens if my pattern takes too long?

Related Tools

JSON Formatter

CSV to JSON