WhySlow

Finds out why a website feels slow. Shows a load snapshot and exports an AI-ready Markdown report to paste into an assistant.

Is a website slow, and you don't know why? WhySlow measures the page, shows you the headline numbers, and writes a report you can paste straight into an AI assistant to work out the cause. HOW IT WORKS 1. Open the page you want to check and click the WhySlow icon. 2. Click "Reload & analyze" for a realistic first-visit test, or "Analyze tab" for what is already loaded. You can also type any address under "Test URL". 3. Read the snapshot, then copy the AI report and paste it into Claude, ChatGPT, Gemini or any other assistant. The report already contains instructions, so there is nothing to write. WHAT YOU GET • A quick snapshot: server response (TTFB), first paint, main content, layout shift, requests, total size, third-party share, render-blocking files, script blocking time, domains and DOM size, each rated good, needs improvement or poor. • The most likely causes of slowness, ranked, with evidence and file names. • An AI-ready Markdown report: a built-in prompt, test context, ranked findings, where time and bytes go, the slowest and largest files, and an honest "limits of this data" section so the AI doesn't guess. • One-click example questions: why is it slow, explain it simply, WordPress/CMS angle, a message to send your host or developer. • Fix and retest: every run is saved on your device. After you change something, WhySlow shows what improved, what got worse, which findings were fixed, and which files appeared or disappeared. Small differences within normal load-to-load variation are marked as unchanged. Add a note ("enabled page cache") and it goes into the report so the AI knows what you changed. • Exports: Markdown report, copy to clipboard, and CSV of every request. • Light and dark themes, with a switch in the popup. Auto follows your system. PRIVATE BY DESIGN WhySlow has no servers, no account, no analytics and no ads. All measuring and all saved history stay in your browser. The only things that leave are the reports you choose to copy or download. GOOD TO KNOW • Timings come from your own browser and connection. Repeat the test and compare rather than treating one run as exact. • Server-side causes (database, CMS, PHP) can only be inferred from the server response time. The report says so. • Chrome blocks extensions on chrome:// pages and the Chrome Web Store.