API Development Tools
A curated collection of free, browser-based tools for every stage of API development — from testing REST endpoints and debugging WebSocket connections to encoding JWT tokens, editing OpenAPI specs, formatting URL parameters, and converting data payloads. All processing happens client-side; your data never leaves your browser.
REST & HTTP
Test REST APIs and debug WebSocket connections directly in your browser. Send HTTP requests, inspect responses, and validate real-time communication.
REST API Client
Send HTTP requests, inspect responses, and test REST APIs with a full-featured browser-based client.
REST API Client / Docs
Learn how to use the REST API Client with guides, examples, and best practices.
WebSocket Client
Connect to WebSocket endpoints, send and receive messages in real time, and debug WebSocket communication.
API Specifications
Design, edit, and validate OpenAPI specifications for your REST APIs. Create API documentation from OpenAPI specs.
Authentication & Tokens
Encode and decode JWT tokens for API authentication. Inspect token headers, payloads, and signatures — all client-side.
JWT Encoder
Create and sign JWT tokens with custom headers, payloads, and supported signing algorithms.
JWT Decoder
Decode and inspect JWT tokens safely in your browser. View header, payload, and signature details.
JWT Encoder / Docs
Learn JWT encoding best practices, signing algorithms, and how to create your first JWT.
JWT Decoder / Docs
Guides for decoding and verifying JWT tokens, understanding claims, and inspecting signatures.
Request & URL Tools
Encode and decode URL parameters for API requests. Handle JSON payloads embedded in URLs for query parameters and route params.
URL Encoder
Encode special characters in URLs for safe transmission in API requests and query parameters.
URL Decoder
Decode percent-encoded URLs back to human-readable format for debugging API requests.
JSON URL Encoder
Encode JSON objects as URL-safe strings for embedding in query parameters and route params.
JSON URL Decoder
Decode URL-encoded JSON strings back to readable JSON objects for inspecting API payloads.
Data Format Tools
Convert and validate API payloads between JSON, YAML, and XML. Format JSON for readability and ensure data integrity before sending requests.
JSON Formatter
Pretty-print and format JSON payloads for readability when working with API responses and request bodies.
JSON to YAML
Convert JSON API payloads to human-friendly YAML for configuration files and API specs.
JSON to XML
Transform JSON data into well-structured XML for SOAP APIs and legacy data interchange.
YAML to JSON
Convert YAML configurations and API specs back to JSON for programmatic processing.
XML to JSON
Convert XML API responses and documents into JSON for easier client-side processing.
JSON Validator
Validate JSON payloads for syntax errors before sending API requests or processing responses.
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