It is a playground for building and testing a pattern before you paste it into whatever you are working in, with flag toggles and code snippet export. The cheat sheet notes where dialects differ.
Yes - live match highlighting plus a capture group inspector, and a find-and-replace preview before you commit to anything.
Yes, patterns can be saved and reused, and there is a built-in cheatsheet alongside multi-line test input.
macOS. Common pitfalls are collected in common regex mistakes.
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