Developer tools

Regex, cron, subnets, status codes and the rest of the lookups. Free to use, no sign-up needed.

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15 tools

Regex TesterTest a regular expression against your own text and see every match and group. Chmod CalculatorTurn 755 into rwxr-xr-x and back, with a plain sentence for each of the three. Cron Expression ExplainerPaste a crontab line and read back, in words, exactly when it runs. IPv4 Subnet CalculatorGive an address and a prefix and get the network, mask, broadcast and host range. IP to DecimalConvert an IPv4 address into the single number and hex value behind it. Decimal to IPTurn a 32-bit number, decimal or hex, back into a dotted IPv4 address. IP Range ExpanderList every address between two IPv4 addresses, one per line. IBAN ValidatorCheck a bank account number against its own check digits before you use it. HTTP Status CodesLook up what a status code means, by number or by name, with what it implies. MIME Type LookupFind the content type for a file extension, or the extensions for a type. User Agent ParserRead the browser, engine, system and device out of a user agent string. Email NormalizerReduce addresses to one canonical form so duplicates stop hiding from you. Safelink DecoderUnwrap the real address hiding inside a mail filter or tracking redirect. Math EvaluatorWork out an expression per line, with brackets, powers and the usual functions. Password Strength CheckerSee how many bits of entropy a password really has, and how long it survives.

Good to know

Where do I start?

Enter the value described above the input. Use Try an example where available to see the expected format, then adjust the options for your task.

How do I use the result?

Review the output, then copy it or download a text file. Input formatting and selected options can change the result.