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Text & Data

Regex Tester Online

Write a pattern, set the flags, and see every match in your sample text.

Updated

Pattern

—

Replacement

amp; or replacement text" value=""/>

Matches (0)

This tool runs in your browser. No account or signup is required.

Common Regex Tester tasks

Developers typically reach for this page when they need to test a regular expression online; debug a regex pattern; find matches and capture groups. The tool is built for quick, practical work rather than a generic demo.

What matters in a regex tester workflow

When developers compare online tools for this job, the useful capabilities tend to center on live matches, flags, captures, replacement, explanations. This page keeps those practical needs in mind while linking to related tools when a different workflow is a better fit.

What is Regex Tester?

Regex Tester runs your pattern against your text using the JavaScript RegExp engine and lists the matches.

What problem does it solve?

Regex is hard to get right without feedback. Testing in your app means rebuilding and rerunning every time you tweak the pattern.

How to use Regex Tester

  1. Enter a pattern and flags (g is on by default).
  2. Paste the text to search.
  3. Run the test and review the matches. An invalid pattern shows the error message.

Example

Pattern and text

Pattern: \d+   Flags: g
Text: order 66 and 42

Matches

66
42

What you can do with Regex Tester

  • Regex tester online
  • Test a regular expression
  • JavaScript regex tester

Common use cases

  • Checking a pattern before using it in code
  • Extracting numbers or IDs from log lines
  • Debugging a regex that matches too much

Related developer tasks

  • Regex tester online
  • Test a regular expression
  • JavaScript regex tester

Regex tester example

Pattern: \d{4}-\d{2}-\d{2}   Flags: g
Text: 2026-10-05 and 2025-01-31

// matches
2026-10-05  (index 0)
2025-01-31  (index 15)

Regex flags and common errors

  • The g flag is required. Without it the test throws an error, so keep g in the flags box.
  • i ignores case, m makes ^ and $ match at each line, and s lets . match line breaks.
  • The tester lists each match and its index. It does not display capture groups.
  • It uses the JavaScript regex engine, so lookbehind and named groups depend on your browser.

Related: Regex Generator, Text Counter, Diff Checker

Regex Tester FAQ

Which regex flavor is this?

JavaScript (ECMAScript). Other languages differ in details such as lookbehind support and named groups.

Why does a global match return nothing?

Check the pattern and flags. An escaped backslash, a missing flag or a typo is the usual cause.

Why do I get an error about a non-global RegExp?

The tool finds all matches, which requires the g flag. Add g to the flags field.

Looking for something else? Browse all developer tools.

onlinedevelopertool.com is a collection of 54 free, browser-based utilities for the small jobs that interrupt real work: formatting a JSON response, decoding a token, converting a timestamp, generating a UUID or checking a hash. Each tool has its own page with a short explanation, a worked example and answers to common questions, so you can use it and learn what it does at the same time.

There is no account to create and nothing to install. Tools run in your browser, so the text you paste is processed on your own device. The one exception is the Website Status Checker, which sends a request from your browser to the address you enter.

Three steps: paste your input, click the tool, copy the result, all inside your browser
Popular developer utilities: JWT decoder, UUID generator, Base64 decoder, SHA-256 hash, regex tester and timestamp converter

What you can do here

  • JSON Tools

    Format, validate, beautify and minify JSON, generate C#, TypeScript, Java, Python, Go, PHP and Kotlin models from it, or convert between JSON, YAML and CSV.

  • Encoders & Decoders

    URL, Base64 and HTML encoding and decoding, plus a JWT decoder for reading token claims.

  • Generators & Hashes

    Generate UUIDs and JWTs, validate UUIDs, and create MD5, SHA-256 and SHA-512 hashes.

  • Web Tools

    Timestamps, color codes, query strings and cron expressions - the small things web work keeps throwing at you.

  • Text & Data

    Format XML and YAML, count text, change case, make slugs, test regex, diff two texts and convert number bases.

  • Website Checking

    Check whether a website or URL is reachable from your browser.

Quick developer reference

  • JSON

    Keys and strings must use double quotes, and trailing commas and comments are not allowed. Those are the three most common reasons a payload fails to parse.

    Validate JSON

  • JWT

    A JSON Web Token is three Base64URL parts joined by dots: header, payload and signature. Decoding shows the claims but does not prove the token is genuine; only signature verification does.

    Decode a JWT

  • Base64

    Base64 is an encoding, not encryption. Anyone can reverse it, and it makes data roughly one third larger, so never use it to hide secrets.

    Decode Base64

  • UUID

    A version 4 UUID is made of random bits and written as 8-4-4-4-12 hexadecimal characters. Collisions are astronomically unlikely, which is why they work well as identifiers.

    Generate a UUID

  • Timestamps

    A Unix timestamp counts time since 1 January 1970 UTC. Ten digits usually means seconds and thirteen digits usually means milliseconds.

    Convert a timestamp

  • Hashes

    MD5 is fine for quick checksums but is not safe for security. Prefer SHA-256 or SHA-512, and remember that hashing is one-way and is not encryption.

    Create a SHA-256 hash

Missing a tool you need? Visit the contact page and tell us what you reach for most often. You can also browse every tool or read the About page to see how the site is built and what it does with your data.