Regular expression tester

A precise tool for crafting, testing, and debugging regular expressions against sample text for developers and data engineers.

Tool coming soon!

We're working hard to get this tool ready for you.

Request Feature / Support

552+

Total Calculations Run

< 15ms

Browser Execution Speed

100%

Client-Side Privacy

4.9 / 5.0

User Satisfaction

AI Web Tool Generator

Build Your Own Custom Web Calculator in Seconds

Type what tool or calculator you need below. Our AI will build it instantly for your site.

About This Tool

The Regular Expression Tester provides an interactive environment to craft and validate regex patterns against sample text. It targets software developers, QA engineers, data scientists, and IT professionals who write or audit patterns and need immediate feedback.
Conceptually, users provide a pattern, test string, and optional flags. The engine compiles the pattern for the chosen flavor and returns all matches, along with capture groups, indices, and the full matched value. Results update as inputs change.
Unique value lies in explicit visibility of capture groups and precise span positions, enabling quick rule refinement and documentation. It supports multiple flavors (ECMAScript/JavaScript, Python, PCRE) and flags like g, i, m, s where applicable.
Core features include pattern input, test text input, flag and flavor selection, live match visualization, group extraction, and error hints. Typical use cases include input validation patterns, log parsing, data extraction, and text transformation tasks.

Save your calculation history with a free account

How to Use

Provide inputs: pattern and test text.
Select flavor and any flags (e.g., g, i, m).
Run to view all matches, with captured groups and indices.
Adjust the pattern and re-run until results align with expectations.
Save the test case or export the results for documentation.

Frequently Asked Questions

Find Quick Answers

Which regex flavors are supported?

Supported flavors include ECMAScript/JavaScript, Python, and PCRE. Each flavor applies its own syntax rules and default behavior for anchors, greediness, and Unicode handling. Users should choose the flavor that matches their runtime environment to obtain accurate results.

Can I test multiple patterns or test strings at once?

The tool tests one pattern against one test string per run. You can create multiple test cases by duplicating the test setup and running them sequentially to compare behaviors across patterns.

How are zero-length matches handled?

To prevent infinite loops, the tester advances the search position when a zero-length match occurs, ensuring progress and continued evaluation of subsequent text.

Is there a limit on input size?

There is no fixed hard limit, but performance depends on browser resources. Very long strings may require more processing time, and large capture sets can produce substantial output.

Need to run multiple calculations?

Create a free account today to unlock unlimited daily runs, access advanced parameters, save your history, and request custom features.

Related Tools

Other useful calculators and utilities you might like

Spotify to MP3 Converter

Convert Spotify tracks and playlists to MP3 format instantly with our free online converter.

Road Distance Calculator

Calculate the driving distance and travel time between two addresses with our free online road dista...

Age Calculator

Calculate your exact age in years, months, and days from any birth date to any target date.

Currency Converter

Convert currencies instantly with real-time exchange rates and historical data support.

Your Feedback Matters

Help Us to Improve