RegexTester.dev
Free online regex tester for real-time pattern matching
Lets developers test and validate regular expressions against sample strings in real time, switching across JavaScript, Python, Java, .NET, Go, Rust and PCRE flavors to catch bugs early.
Built by Fu liang · Developer Tools · Software Engineering · Free
In category: #977 of 989 · Developer Tools
RegexTester.dev is a Community listing on Launch Llama with 0 total upvotes, founded by Fu liang who joined in Nov 2026, compared against 6 alternatives.
Community listing
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Fu liang (Joined Nov 2026)
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Compared against 6 alternatives
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Launched on Launch Llama Nov 9, 2026 · #94 of 96 that day
About
The tester runs in the browser with no signup or cookies, showing match counts, highlighted results, and active flags such as global and case-insensitive as you edit. A quick reference panel lists common tokens, anchors, meta sequences, quantifiers and character classes, and it includes ready-made samples such as an email address and a phone number pattern. The site also offers a step-through debugger for backtracking, a benchmark suite for comparing patterns, and a cross-engine compatibility checker that covers seven engines.
Key Features
- Highlights regex matches in real time as you type a pattern and sample text
- Switches between JavaScript, Python, Java, .NET, Go, Rust and PCRE flavors
- Steps through regex backtracking with the Regex Debugger to find failing paths
- Checks one pattern's behavior across seven engines with the Compatibility tool
- Benchmarks competing patterns side by side in the Regex Benchmark Suite
- Saves and shares patterns, test strings and replacements with Save and Share
Use Cases
- Debugging why a validation regex fails on certain email or phone number inputs before deploying it
- Comparing one pattern's behavior across JavaScript, Python, and Go before porting code between languages
- Checking regex unit tests and replace rules against sample strings before committing code
From the founder
Who it's for
“Developers and QA engineers who ship regexes across languages — JavaScript, Python, Go, Rust, Java, .NET or PCRE2 — and need to catch flavor differences before they hit production.”
Why I built it
“I kept breaking patterns by moving them between services in different languages: lookbehind support, \w semantics and atomic groups all differ. I built a tester that runs real WASM builds of eight engines side by side, with a step-through debugger and a compatibility checker, so the divergence shows up before the code review does.”
Who it is for
- Developers writing or debugging regular expressions in JavaScript, Python, Java, .NET, Go, or Rust
- Engineers verifying that one pattern behaves the same across multiple regex engines
Pricing
RegexTester.dev is free to use. See the website for details.
Alternatives
JomatterBrowser-based toolkit for formatting, minifying, validating, and analyzing HTML, CSS, and JavaScript code. No signup required.
JavaScript ToolsFor developers: JavaScript Tools provides privacy-first utilities for code formatting, JSON inspection, and test fixture generation so you work faster locally.
RealAppTestersFor Android developers: RealAppTesters provides real testers to meet Google Play's 12-tester requirement, reducing rejection risk and accelerating production approval.More in Developer Tools
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