RegExr vs Retest

RegExr is a free web tool for learning, building, and testing regular expressions. It supports JavaScript and PHP/PCRE expressions, with results that change as you type. Hovering over a match or expression reveals details, and the Explain tool describes an expression in plain English. Tests mode lets users assemble examples that an expression should match or reject. Replace and List produce custom outputs, while Details shows capture groups. Learning resources include a cheatsheet, reference, help pages, and examples. Users can search and rate Community Patterns, then save and share expressions. Signing in keeps favorites and patterns in My Patterns. A saved expression gets a public link, and a Community-shared copy cannot be edited or deleted. The listed RegExr plan costs nothing. The project README credits Grant Skinner and gskinner.com as creators and identifies this version as GPL v3 licensed. It directs issue and feature requests to GitHub and regular-expression questions to Stack Overflow.

Retest is a free, open-source terminal utility for developing and checking regular expressions on Linux. A subject string can be supplied as an argument or piped through standard input, so it can fit into shell workflows. Retest finds all non-crossing matches and highlights nested capture groups in colors distinct from the whole match. An optional formatted list shows match order and string indexes. Release 0.2.2 added a flag for reading the subject from a file. The project provides Linux release binaries, including a 64-bit Debian installer listed for release 0.2.2. Its README describes compiling from source with Cargo and installing through a Makefile. The source code and documentation are licensed under Apache License 2.0. The project presents Retest as a terminal-based alternative to regex101, for developers building and checking patterns. No paid plans or usage limits are listed.