Developer Tools calculators

Format JSON into clean, readable indentation locally.

Check JSON syntax and see clear parsing errors locally.

Remove optional whitespace from valid JSON.

Encode Unicode text as standard Base64.

Decode valid Base64 into Unicode text.

Percent-encode text for use in a URL component.

Decode percent-encoded URL text safely.

Generate one or more cryptographically random UUID v4 values.

Convert Unix timestamps and readable dates.

Decode JWT headers and payloads locally without verification.

Test JavaScript regular expressions and capture groups.

Calculate Subnet step by step: Network = address AND mask; broadcast = network OR wildcard; usable hosts = 2^(32 − prefix) − 2.

Calculate IBAN Validator step by step: Move the first four characters to the end, convert letters to numbers (A=10 … Z=35), then the number mod 97 must equal 1.