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Explore Boad App Store What is the Online Regex Tester & Debugger?
Boad Tools Regex Tester is a client-side regular expression editor that validates syntax in real-time, displays live match highlights and capture groups, and tests string substitutions.
Why use client-side regex testing?
Regular expressions often contain private user tokens, sample PII (emails, names, phone numbers), or sensitive database dumps. Uploading these strings to third-party web servers introduces unnecessary privacy risks.
Boad Tools runs native JavaScript V8 regular expression evaluation 100% locally on your machine. Your input strings never leave your browser, providing zero latency and ironclad data privacy.
How to use this tool
- Input your pattern: Type your regular expression between the slashes. If syntax errors occur, an alert banner will explain what to fix.
- Select Flags: Toggle flags like g (find all matches), i (case-insensitive), or m (multiline).
- Test with Text: Type or paste your sample text in the left panel. Matches will immediately glow with highlight indicators.
- Inspect Groups: The Matches tab breaks down match indices and numbered capture groups ($1, $2, etc.).
- Test Replacement: Switch to the Replace tab to preview text replacement using tokens like $& or $1.
- Use Presets: Quickly load common patterns for emails, URLs, IP addresses, dates, and UUIDs with one click.
Frequently Asked Questions
It uses the official JavaScript ECMAScript RegExp engine embedded directly in your modern web browser, matching the standard behavior in Node.js, Next.js, and browser JavaScript.
The 'g' (global) flag ensures the engine continues searching for all occurrences across the entire text instead of stopping after the first match.
Yes! In the Replace tab, use $1 for the first captured group, $2 for the second, and $& for the entire match string.
No. The tool processes strings entirely in your browser memory, with protection against infinite regex loops on zero-length matches.