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Client-Side Regex Workbench & Tester

Zero Egress

Build, test, and debug regular expressions with real-time match highlighting, group extraction, substitution preview, and code generators. 100% in-browser zero egress.

Sample Regexes:
//g
Test String(97 chars, 3 lines)
Visual Match HighlightingClick any match to view its capture groups
(00)300123451234567899 (01)00012345678905(10)LOT-2026A(17)261231 (400)PO-987654(410)9501101020917
Match Details6 matches
< 1 ms
Match #1Line 1:1 • pos 0–23
(00)300123451234567899
Capture Groups:
$ai:"00"
$value:"300123451234567899 "
Match #2Line 2:1 • pos 23–41
(01)00012345678905
Capture Groups:
$ai:"01"
$value:"00012345678905"
Match #3Line 2:19 • pos 41–54
(10)LOT-2026A
Capture Groups:
$ai:"10"
$value:"LOT-2026A"
Match #4Line 2:32 • pos 54–65
(17)261231
Capture Groups:
$ai:"17"
$value:"261231 "
Match #5Line 3:1 • pos 65–79
(400)PO-987654
Capture Groups:
$ai:"400"
$value:"PO-987654"
Match #6Line 3:15 • pos 79–97
(410)9501101020917
Capture Groups:
$ai:"410"
$value:"9501101020917"
Zero Data Egress Guarantee: All regular expression evaluations, capturing group extractions, and substitutions are processed 100% in local browser memory via JavaScript V8 engine. Test strings, database connections, authorization tokens, and server logs are never sent to external servers.
Architectural Privacy Guarantee

Real-Time Regular Expression Playground & Token Inspector

Test, debug, and analyze JavaScript regular expressions with real-time match highlighting, capture group extraction, and replacement preview. Inspect regex performance safely without data leaks.

In-Browser Technology:Native ECMAScript RegExp EngineCapture Group TokenizerSyntax HighlighterReplacement Previewer

How Client-Side Processing Works

Every step executes within your browser runtime without network calls or cloud storage.

  • 1Patterns and flags (g, i, m, s, u, y) are compiled using the browser's high-performance V8/SpiderMonkey regex engine.
  • 2Test text matches are highlighted with designated color-coded indices.
  • 3Capture groups and named groups are parsed into structured inspection tables.
  • 4Replacement pattern substitutions preview output in real time.

Common Workflows & Use Cases

Validating Sensitive Customer Formats

Test regex patterns for tax IDs, credit cards, emails, and phone numbers using actual customer data without risking data breaches.

Log File Extraction & Parsing

Design and test capture groups to extract IP addresses, timestamps, and status codes from server log snippets.

Data Cleansing & String Replacement

Test complex search-and-replace expressions to reformat messy text exports prior to database ingestion.

Learning & Debugging Complex Patterns

Understand lookarounds, non-capturing groups, and greedy/lazy quantifiers with visual feedback.

Questions & Answers

Frequently Asked Questions

Is my test data uploaded to any server?

No. All regex compilation, matching, and replacement previewing take place locally inside your browser thread.

Which regular expression engine is used?

It uses your browser's native ECMAScript RegExp implementation, ensuring 100% fidelity with modern JavaScript, Node.js, and browser runtimes.

Are named capture groups supported?

Yes. Modern JavaScript named groups (e.g. (?<name>...)) are fully supported and displayed in the capture group inspector.

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