Debug & Review · LOCAL TOOL

Regex Bench

Exercise a regular expression against text you control, inspect match ranges and capture groups, and preview a replacement without changing the original input.

Runs in this page
No API call

WORKSPACEINPUT → RESULT

Your input

LOCAL

Result

Run the tool to see a result.

Your result will appear here. Input is not saved.

Browser-side processingNothing is sent to a tool API.

WHY THIS TOOL EXISTS

A focused job, not a black box.

Each match includes start and end offsets so you can relate a result back to the source. The runner is isolated and has input, match-count, and time limits.

How to use it

Enter a pattern and supported flags.
Paste test text and an optional replacement.
Review matches, groups, and the replacement preview.

TRY A WORKING EXAMPLE

Start with known input.

Load this sample into the workspace, run the tool, and compare the result shown below.

Show sample input

{
  "pattern": "\\b(cat|dog)\\b",
  "flags": "gi",
  "text": "A cat and a dog.",
  "replacement": "pet"
}

Expected sample result from the local tool

2 match(es) · JavaScript string offsets.

{
  "matches": [
    {
      "index": 2,
      "end": 5,
      "text": "cat",
      "groups": [
        "cat"
      ]
    },
    {
      "index": 12,
      "end": 15,
      "text": "dog",
      "groups": [
        "dog"
      ]
    }
  ],
  "replacementPreview": "A pet and a pet."
}

LIMITS AND INTERPRETATION

What the result cannot tell you.

The syntax follows JavaScript RegExp. Large or pathological expressions are terminated; Unicode offsets use JavaScript string indexing.

Inputs are processed in this page and are not written to local storage.