Developer Tools Calculators
Twenty browser utilities for payloads, checksums, and CSS. Pretty-print JSON or SQL, convert CSV, parse cron, check WCAG contrast, or decode a JWT.
Available calculators in Developer Tools (20)
JSON Formatter
Beautify, minify, and validate JSON without sending it to a server.
Base64 Encoder / Decoder
Encode or decode UTF-8 text as RFC 4648 Base64.
URL Encoder / Decoder
Percent-encode or decode a URL component.
UUID Generator
Generate cryptographically random UUID version 4 strings.
Hash Generator
Hash text with SHA-1, SHA-256, SHA-384, SHA-512, or MD5.
JWT Decoder
Decode a JSON Web Token header and payload locally.
Regex Tester
Test a JavaScript regular expression and list every match.
Meta Tag Generator
Build title, description, Open Graph, and Twitter meta tags.
SERP Preview
Preview a title, URL, and description as a search snippet.
HTML Encode / Decode
Escape or unescape HTML entities for &, <, >, and quotes.
CSV to JSON Converter
Convert CSV tables to JSON objects and back.
XML Formatter
Pretty-print XML tags in the browser.
YAML to JSON Converter
Move simple maps and lists between YAML and JSON.
SQL Formatter
Break a query onto keyword lines.
Cron Expression Parser
Show the next fire times for a cron expression.
IBAN Validator
Check an IBAN with the ISO 13616 MOD-97 checksum.
Luhn Checksum
Test a Luhn check digit for QA PANs and IDs.
Color Contrast Checker
Measure WCAG contrast between two hex colors.
CSS Gradient Generator
Build a two-stop linear-gradient snippet.
Box Shadow Generator
Tune offset, blur, spread, and color for box-shadow.
Frequently Asked Questions — Developer Tools
Do tokens leave the device?
No. JWT decode and hashing stay in the browser.
Is the JWT signature verified?
The decoder shows claims only. Treat them as untrusted unless you verify the signature yourself.