Regex Group Visualizer

How to use this developer tool

1. Enter sample text containing at least one match.
2. Provide the pattern and flags without slash delimiters.
3. Visualize the first match and inspect each group value.
4. Use start and end offsets to check nesting and boundaries.

What this developer tool does

The report maps the full match and each capture group to its value and, when available, its exact span in the source text.

Capture groups show the last value captured when a quantified group repeats.

Example

Pattern: (a(b))
Text: ab
Group 0: ab; Group 1: ab; Group 2: b

Use cases

• Debug nested groups.
• Teach capture numbering.
• Verify optional and alternative branches.

Tips for reliable output

• Use noncapturing (?:...) when a group needs no value.
• Name important groups.
• Add d for exact indices in modern browsers.
• Test optional branches with several inputs.

Processing details

Group zero is the full match. Numbered groups follow opening-parenthesis order; named groups are reported with their names when the engine exposes them.

Only the first match is visualized to keep the group structure focused. Browser support controls whether exact subgroup indices are available.