D2D Utilities
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Regex Tester & ReDoS Guard

1,000ms ReDoS Worker Guard

Test, validate, and debug regular expressions with capture groups, live replacement preview, and 1,000ms ReDoS worker protection.

Client-Side Evaluation: Patterns and text never leave browser memory
//g
Flags:
Matches Breakdown
3 matches 0.19ms
Match #1index: 13 (19 chars)
"support@example.com"
$1:"support"$2:"example.com"user:"support"domain:"example.com"
Match #2index: 36 (16 chars)
"admin@domain.org"
$1:"admin"$2:"domain.org"user:"admin"domain:"domain.org"
Match #3index: 98 (16 chars)
"sales@store.net."
$1:"sales"$2:"store.net."user:"sales"domain:"store.net."
Replace Preview

ReDoS Protection & Evaluation

Pathological regular expressions with overlapping nested quantifiers (such as (a+)+$) can cause exponential backtracking, freezing the browser. This tester isolates evaluation in a dedicated Web Worker with a strict 1,000ms hard deadline.

How to test regex expressions safely

  1. 1Enter your regular expression pattern and select active flags (g, i, m, s).
  2. 2Provide test target text to evaluate matches in real time.
  3. 3View capture group breakdowns and replacement preview outputs.

Frequently Asked Questions

What is ReDoS protection?

A background Web Worker terminates any runaway exponential regex after 1000ms to prevent browser freezes.