Interactive Regex Tester
Live Match & Highlights
About Interactive Regex Tester
An interactive regex tester provides real-time visualization of regular expression matching against target text inputs, highlighting capture groups and syntax components.
How It Works
The tester compiles your regex dynamically with flags (Global, Case Insensitive, Multiline) and matches it against your test string. It calculates character offsets for matching hunks and highlights them with clean colored overlays.
How to Use Interactive Regex Tester
- Type or paste your regular expression pattern in the top pattern input box.
- Toggle any desired regex flags (such as Global 'g', Case Insensitive 'i', or Multiline 'm').
- Insert your test string in the text container below to view real-time highlighted matches.
- Hover over any highlighted match segment to see details of its capture groups and character ranges.
FAQ
Which regex flavor is used?
JavaScript (ECMAScript) regex. Most PCRE features have direct equivalents — but features like lookbehind have nuance, which the explainer calls out.
Why does my pattern hang the browser?
Catastrophic backtracking. Look for nested quantifiers like `(a+)+`. The tester guards against this by timing out long-running matches.
Under the hood
Constructs `RegExp` with the configured flags, executes inside a Web Worker with a hard time budget, and streams capture group offsets to the highlighter. Match ranges are rendered with overlapping span layers so highlights remain correct even when groups intersect.
Engineered by HaorGrix