Web Vitals

Inspect React component trees

Official browser extension by Meta for inspecting and debugging React component trees, props, state, hooks, and context in real-time. Features component highlighting on hover, profiler for measuring render performance and identifying bottlenecks, and component search/filtering. Supports React 16+ including Suspense, error boundaries, and concurrent features. Available for Chrome and Firefox. Essential for debugging re-renders, state management issues, and understanding component hierarchies.

Debug Vue.js applications

Official browser DevTools extension for Vue.js providing deep inspection of component trees, reactive state, props, events, and slots. Includes Pinia/Vuex store debugging with time-travel, Vue Router inspection, performance timeline, and component highlighting. Works with Vue 2 and Vue 3. Available for Chrome and Firefox with standalone Electron app. Essential for debugging reactivity and understanding component hierarchies in Vue applications.

Responsive web development tool

Open-source browser for responsive web development that shows multiple device viewports simultaneously with synchronized scrolling, clicking, and navigation. Preview your site on phone, tablet, and desktop sizes side by side in real-time. Features screenshot capture for all viewports, element inspector, network monitoring, and hot-reload support. Built on Chromium. Free alternative to Polypane for developers who need quick responsive testing without paid subscriptions. 23K+ GitHub stars.

Test and debug MCP servers before they ship

Open-source platform for inspecting, debugging and regression-testing MCP servers, MCP Apps and ChatGPT apps, with OAuth and protocol conformance for local and CI workflows.

Automatically detect and fix slow React re-renders

Open-source tool that highlights unnecessary and slow React re-renders directly in your app — as a browser extension, CLI, or drop-in package, with no code changes required.

Open-source MCP bridge between AI assistants and the Unity Editor

MCP for Unity is CoplayDev’s MIT-licensed bridge between MCP-compatible AI assistants and the Unity Editor. It exposes tools for assets, scenes, GameObjects, scripts, tests, profiling, and build-oriented workflows. The community project supports Unity 2021.3 LTS through 6.x and is explicitly not affiliated with Unity Technologies.

Sentry-maintained MCP server and CLI for Xcode builds, simulators, and tests

XcodeBuildMCP is a Sentry-maintained, MIT-licensed MCP server and CLI for agent-assisted iOS and macOS development. It lets MCP-compatible coding agents run Xcode build and test workflows, manage simulators, inspect failures, and work through Homebrew, npm, or on-demand client configuration, with documented Sentry telemetry controls for teams that need an opt-out.

Open-source diagnostic for AI operational misalignment

iFixAi is an Apache-2.0 diagnostic tool for scoring AI agents and models against operational-misalignment risks such as hallucination, manipulation, sabotage, sandbagging, and oversight evasion.

UK AI Security Institute framework for LLM safety evaluations

Inspect AI is an MIT-licensed framework from the UK AI Security Institute for running large language model evaluations, including tool use, multi-turn dialogue, model-graded scoring, and reusable evaluation tasks.