Show HN: PromptLab – Local-first Chrome sidepanel for LLM prompt testing

PromptLab, a local-first Chrome extension for testing LLM prompts, was released on Hacker News. The Manifest V3 side panel, built with React, TypeScript, and Vite, stores up to 20 prompt fixtures entirely in chrome.storage.local with no analytics, remote APIs, or cloud storage, ensuring data never leaves the machine.

Chrome extension Manifest V3 for managing local prompt fixtures. Nothing leaves the machine: no analytics, no remote APIs, no cloud storage. - React + TypeScript + Vite - Tailwind CSS @crxjs/vite-plugin for the extension build chrome.storage.local in the extension, localStorage in the browser preview npm install npm run dev Opens a local dashboard at http://localhost:5173 . Add, edit, and delete up to 20 prompt fixtures. Run Eval is a stub for tomorrow’s LLM wiring. npm run build Then in Chrome: - Open chrome://extensions - Enable Developer mode - Click Load unpacked - Select the dist folder Click the extension icon to open the side panel. For live reload while developing the extension: npm run dev:extension Load the generated dist folder as unpacked. Keep the Vite process running. - Fixtures persist only in chrome.storage.local or localStorage in the web preview - No telemetry, fonts-from-CDN, or outbound requests in this app - Permissions: storage , activeTab , and sidePanel needed to host the dashboard