Wappalyzer

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.

Open-source desktop AI coworker for browsing and code execution.

Accomplish Coworker is an MIT-licensed open-source AI coworker that runs on the desktop, combining computer-use style browsing with code execution so agents can research, implement, run, and debug workflows in one local environment.

Apple's Safari-native MCP server for web debugging agents

Safari MCP Server is Apple's safaridriver-based MCP server in Safari Technology Preview, giving compatible coding agents local access to Safari page content, console logs, network requests, screenshots, JavaScript evaluation, interactions, viewport controls, and accessibility/performance checks.

Open-source agentic browser that runs local AI agents in your browsing workflow.

BrowserOS is a privacy-first, open-source agentic browser for running AI assistants locally inside real browsing sessions instead of handing every task to a remote cloud browser.

Microsoft browser agent that turns long-horizon web tasks into reusable Playwright code

Webwright is a Microsoft browser-agent project that asks coding models to write, debug, and reuse Playwright scripts instead of relying on one-off stochastic click loops. The approach gives automation teams a more inspectable artifact: scripts can be logged, reviewed, rerun, and maintained like normal test or scraping code. It is especially relevant for long-horizon browser tasks where teams care about determinism, auditability, and resilience to UI changes.

One tool for intercepting, mocking, and replaying HTTP — acquired by BrowserStack

Requestly is a BrowserStack-backed API client, HTTP interceptor, mock server, and session replay tool for frontend and QA teams. Its current product is commercial/API-client led, while the legacy interceptor/open-source code is AGPLv3. The free plan covers individual workflows, and Pro lists at $12/user/month monthly or $9/user/month annually for collaborative QA and frontend debugging teams.

Visualize JSON, YAML, XML, and CSV as interactive graphs

JSON Crack transforms structured data files into interactive, visual graphs that make complex nested data easy to understand. Paste or import JSON, YAML, XML, CSV, or TOML and instantly see the data as a navigable node graph with collapsible sections, search, and path highlighting. All processing happens client-side with no server storage.