Regex101 is a tool to **build, test, and debug regex**.

It provides a **Regex Editor** with **Flavor: PCRE2 (PHP)** and modes for **Match**, **Substitution**, **List**, and **Unit Tests**.

Key tools shown by Regex101 include:

- **Code Generator**

- **Regex Debugger**

- **Export Matches**

- **Benchmark Regex**

- **Format Regex**

Regex101 also includes an automatic explanation and match details:

> An explanation of your regex will be automatically generated as you type.

> Detailed match information will be displayed here automatically.

The editor includes a **Quick Reference** with categories such as **All Tokens**, **Common Tokens**, **General Tokens**, **Anchors**, **Meta Sequences**, **Quantifiers**, **Group Constructs**, **Character Classes**, **Flags/Modifiers**, and **Substitution**.

The source material does not show an official self-hosting option, deployment documentation, or resource requirements; it is presented as an online regex editor with save, share, account, community patterns, and quiz features.