# Regular Expression Tester

Inspect bounded PCRE matches and capture groups on a UTF8 text sample.

[Open this tool](https://whatson.pk/developer-regex-calculator/)

Category: Developer & Data

A pattern needs representative examples before it is used on a real dataset.

Test a small UTF8 sample and inspect matches, groups and byte positions.

## Inputs and controls

* Pattern body. Enter the body without delimiters. UTF8 mode is always enabled.
* Modifiers: Unicode; Unicode, ignore case; Unicode, multiline; Unicode, ignore case and multiline; Unicode, dot matches newline; Unicode, all three modifiers
* Text to inspect

## How to use

* Choose modifiers. Enter pattern body.

* Paste or enter text to inspect.

* Select Process input. Read the returned values alongside the assumptions below before copying, exporting or acting on the result.


## Why use this tool

Bounded PCRE matching keeps the test focused and exposes captured values.


## Before relying on the result

Up to 100 matches. Byte offsets are shown. Backtracking and recursion limits bound work; this is PCRE, not JavaScript regex.


## Tool limitations

Up to 100 matches. Byte offsets are shown. Backtracking and recursion limits bound work; this is PCRE, not JavaScript regex.

## Questions

### Will the pattern behave identically in JavaScript?

Not necessarily. This tester uses PHP PCRE, whose rules can differ from JavaScript regular expressions.

### What should I check before using Regular Expression Tester?

Check Pattern body, Modifiers and Text to inspect. Use the exact units shown beside the controls and replace any example values with your own inputs.

Source page last modified (UTC): 2026-10-04T16:58:29+00:00

This profile describes the tool. It does not execute it or supply a professional certification.