RegexPlanet vs Retest

RegexPlanet is a free web service for testing regular expressions during development. It offers separate test pages for engines including Java, Python, Bun, Go, Deno, Erlang, Haskell, MySQL, .NET, Node.js, Perl, PHP, PostgreSQL, Ruby, Rust, Swift, Tcl, XRegExp, and the browser. The Java tester accepts a pattern, replacement, and multiple input strings, with a control for adding more inputs. Options include case-insensitive matching, multiline mode, and Unicode-aware case folding. The home page provides a field for share codes, and the site directs users to Regex Zone for sharing expressions and finding patterns. A status page reports engine status and says each engine runs separately. RegexPlanet warns that malformed expressions may run indefinitely and that some engines or hosts may face denial-of-service attacks. Its privacy policy describes collection of IP addresses, browser data, and form entries; raw logs are stored by Google CloudRun. The service is offered as-is and as-available.

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.