Regex Tester
Provides an interactive environment where users can write a regular expression pattern, test it against sample strings, and view real-time match. Code never leaves your device — formatting and validation run locally in your browser.
How to Use the Regex Tester
Similar Tools You Might Need
See allHex ↔ ASCII Converter
Convert between hexadecimal bytes and ASCII text. Supports custom delimiters and real-time bidirectional conversion. Code never leaves your device — formatting and validation run locally in your browser.
Base64 Encode/Decode
Encodes text or small files into Base64 strings and decodes them back with automatic MIME-type detection for binary safety. Code never leaves your device — formatting and validation run locally in your browser.
HTML Preview
Write HTML and see a live preview rendered in a sandboxed iframe. Perfect for prototyping and testing. Code never leaves your device — formatting and validation run locally in your browser.
Word Counter
Analyzes your writing with real-time word count, character counts with and without spaces, sentence and paragraph counts, plus estimated reading time (200 wpm) and speaking time (150 wpm). Essential for writers, students, and SEO professionals tracking length and pacing.
ROI Calculator
Measures return on investment by comparing net gain or loss against the original cost, expressed as both a percentage and a dollar amount. Essential for marketing campaign evaluation, equipment purchase decisions, real estate investment analysis, and comparing investment opportunities.
Frequently Asked Questions
How does the real-time matching work?
As you type your regex pattern and test string, matches are highlighted instantly. The tool uses the JavaScript RegExp engine, so what you see is exactly how the pattern will behave in your code.
Does it support all regex flags?
Yes. You can toggle common flags like global (g), case-insensitive (i), multiline (m), and dotAll (s) using checkboxes. The flags are applied to your pattern in real time.
Can I test multiple patterns at once?
Enter one pattern at a time, but you can test it against multiple sample strings. Paste different test cases to verify your regex handles all edge cases correctly.
Does it explain what my regex does?
The tool highlights matches visually. For a detailed breakdown of what each part of your pattern means, use a regex explanation tool alongside this tester.
Is my regex pattern stored?
No. Your pattern and test strings stay in your browser and are never transmitted anywhere. Everything runs locally using the regex.js library.
Is there a cap on global matches?
Yes. With the g flag the exec loop stops after 1000 matches (zero-length matches nudge lastIndex forward so it cannot hang); without g only the first match returns. The badge reads N match/matches, and AI generation costs 1 credit per use.
Related Developer Tools
Bulk Regex Extractor & Replacer
Hunt IPs, API keys, emails, and URLs across thousands of logs or code files — extract matches or replace in place. SREs scrub 5,000 logs before sharing — local JS RegExp, 2 free batches a day.
Secret Scanner
Scan text and code for leaked secrets and credentials. Detects Stripe keys, GitHub tokens, Slack tokens, Google API keys, AWS keys, OpenAI keys, JWT tokens, private keys, and config passwords.
Last updated October 2026