Free Developer Tools: Format JSON, Decode JWT & Debug Data
Format and validate JSON, inspect JWT claims, encode URLs and test patterns. Follow practical debugging workflows with free online developer tools.
JSON Formatter
Format, validate, and beautify JSON data
JSON Validator
Validate and format JSON online — instant syntax checking
JSON to TypeScript Converter
Convert JSON objects to TypeScript interface or type definitions
JSONL / NDJSON Formatter & Validator
Validate and format JSON Lines (JSONL / NDJSON) data online — line-by-line error reporting, compact and pretty-print modes
YAML Formatter
Format, validate and minify YAML online. Fix YAML syntax errors instantly in your browser — no signup required.
YAML Validator
Free online YAML validator. Paste your YAML and instantly check syntax, see error line numbers, and preview parsed structure as JSON. No signup needed.
JWT Decoder
Decode JSON Web Tokens securely in your browser
Base64 Encoder/Decoder
Encode and decode text to Base64 format
URL Encoder/Decoder
Encode and decode URLs for safe transmission
Regex Tester
Test and debug regular expressions in real-time
Timestamp Converter
Convert between Unix timestamps and human dates
UUID Generator
Generate unique identifiers (UUID v1 & v4)
Cron Expression Generator
Build and validate cron expressions with a visual editor
How to choose and use these tools
- Validate the input format first. JSON requires double-quoted keys and does not allow trailing commas or comments.
- Format JSON for inspection, then generate TypeScript from a representative sample. Review optional fields and unions against the actual API.
- Decode a token to inspect its claims or convert an epoch timestamp to a date. Verify signatures and time units separately.
Worked example
The valid JSON sample {"id":1,"active":true} maps to number and boolean fields. The text {id:1,} is a JavaScript-style object, not valid JSON: the key needs quotes and the trailing comma must be removed.
Frequently asked questions
Does decoding a JWT verify it?
No. Decoding exposes the header and payload. Authentication also requires checking the signature, permitted algorithm, issuer, audience and relevant time claims with a trusted library.
Should I format JSON before converting it?
Validate it first so you can distinguish syntax errors from conversion issues. Formatting changes whitespace, not the data model. Generated types describe the supplied sample, not every possible API response.