API Client is part of DevStudio — a free, in-browser collection of developer utilities that work without sign-up, installation, or any backend service. Universal API client — REST, GraphQL, MCP, SSE — environments, collections, scripts, visualizer, all running entirely on your device. Because the page never uploads what you paste, you can run sensitive payloads, configuration files, secrets, or production data through it with confidence: nothing leaves your browser tab. Use API Client for ad-hoc debugging, code review, log triage, release prep, learning a new format, or as a quick scratchpad while you build. If you use this tool a lot, pair it with Webhook Receiver, DB Client, File Browser, and the rest of the DevStudio toolkit for related developer workflows.