jwt.io
jwt.io
Decodes a JSON Web Token into readable header, claims and signature
No sign-upOn device
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regex101.com
Builds and explains a regular expression while you type it.
A regex workbench with live match highlighting, a side pane that explains every token in English, a substitution tester and a debugger that steps through the backtracking. It supports PCRE, JavaScript, Python, Go, Java and .NET flavours separately, which matters because the same pattern genuinely behaves differently in each. Saved patterns get a permanent link, so it doubles as the way to hand a colleague a working example instead of a paragraph of description.
AltFTool does this too
If you would rather not leave the site, Regex Tester covers the same job here — free, no account, and it runs in your browser.
Open Regex TesterQuestions
Works the moment the page loads. No account, no email, no trial. Long inputs and catastrophic backtracking hit an execution timeout rather than completing.
Yes. regex101 sends your input to its own servers to process it. That is fine for public material; for anything containing personal data, use one of the on-device tools instead.
Long inputs and catastrophic backtracking hit an execution timeout rather than completing.
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