JWT Encoder/Decoder

The tool enables precise encoding and decoding of JSON Web Tokens (JWTs) in a developer-focused workflow. It accepts header and payload as JSON, an algorithm, and an optional secret or private/public key pair, performing all operations client-side without server calls. This supports fast token construction for API testing and learning JWT structure. Encoded tokens can be used directly in API clients or gateways, while decoded views aid in auditing token contents and claims.
Conceptually, encoding builds header and payload into a JSON string, applies base64url encoding, and signs the result with the chosen algorithm. Decoding splits a token into header, payload, and signature, decodes each base64url segment, and parses the resulting JSON. The tool reports any JSON syntax errors, invalid base64, or unsupported algorithms and shows the exact header and payload fields to simplify debugging and verification tasks.
Unique value comes from strict JSON validation, deterministic encoding, support for multiple algorithms, and clear error messages that guide debugging. Typical use cases include API security testing, education for developers learning JWTs, and integration testing in CI pipelines. All data remains on the client unless the user explicitly exports the token or results. The tool is sized for quick iterations, lightweight enough for local development, and designed to complement dedicated security libraries.
Core features include input grouping for header and payload, algorithm selector, secret input for signing, operation toggle, real-time or on-demand results, and structured outputs with optional verification.