Regex Tester & Debugger
Test JavaScript regular expressions in real time against sample strings with capture-group inspection and presets for PAN, IFSC, Email, and Mobile.
How the Regex Tester & Debugger works
Test JavaScript regular expressions in real time against sample strings with capture-group inspection and presets for PAN, IFSC, Email, and Mobile. Below is the exact mathematical or algorithmic model used by this programming utility, along with its key operating assumptions.
Compiles RegExp(pattern, flags) and iterates RegExp.prototype.exec() with zero-length match loop protection.Step-by-step workflow
- Paste or type your input string, payload, or expression into the Regex Tester & Debugger editor.
- Your browser executes Compiles RegExp(pattern, flags) and iterates RegExp.prototype.exec() with zero-length match loop protection. locally using native Web APIs without transmitting data over the network.
- Inspect validation diagnostics, byte/character metrics, or formatted output and copy the result in one click.
Worked example & key advantages
Click the 'Indian PAN' preset to test /[A-Z]{5}[0-9]{4}[A-Z]{1}/g against sample payroll strings and inspect every matched token and index.
Why use this Regex Tester tool
- Zero-telemetry local execution—safe for formatting production JSON payloads, tokens, regexes, and hashes.
- Uses standards-compliant browser APIs (RFC 8259 JSON, RFC 4648 Base64, RFC 4122 UUID, SubtleCrypto SHA-2, IANA tzdb).
- Instant feedback with byte-size metrics, line-number syntax diagnostics, and one-click clipboard copy.
Important Assumptions & Scope
- Uses the ECMAScript (JavaScript) RegExp engine built into your browser.
- Caps execution at 200 matches per run to prevent catastrophic backtracking hangs.
Frequently Asked Questions — Regex Tester
Clear answers to common questions about methodology, edge cases, and privacy.
What regex matches an Indian PAN card number?
A standard 10-character Indian PAN follows the pattern ^[A-Z]{5}[0-9]{4}[A-Z]{1}$ (five uppercase letters, four digits, and one check letter).
Is it safe to use the Regex Tester & Debugger with confidential production data?
Yes. The Regex Tester & Debugger executes entirely within your browser tab's memory using native JavaScript and Web Crypto APIs—no payloads, tokens, or strings ever leave your device.
Does the Regex Tester support UTF-8 and multi-line inputs?
Yes. All UtilAxis developer utilities handle multi-byte UTF-8 characters (including ₹, accented characters, and emojis) as well as multi-line payloads without truncation.