Chrome Extension
Performance
Tool.
A Chrome extension that reads the browser's built-in Performance API and surfaces the numbers that matter, TTFB, TTI, DNS lookup, resource waterfall, in a popup. No network requests. No data collection. Everything stays in the browser.
What it measures
Total Requests
Count of all HTTP resources fetched by the page.
Resource Domains
Unique external domains serving content to the page.
Subdomains
First-party subdomains detected in the resource list.
Time to First Byte
Latency from navigation start to first byte received.
DNS Duration
Time spent resolving the page's hostname.
Connection Duration
TCP and TLS handshake time.
Response Duration
Time from first byte received to response complete.
Time to Interactive
Detected via long-task observer: when the main thread goes quiet for 5 seconds.
First Paint
When the browser first renders any pixel on screen.
How it works
A content script runs on every page and observes long tasks via PerformanceObserver to compute TTI. When you open the popup, it sends a message to the active tab requesting its PerformanceNavigationTiming and resource entries, then renders the results locally.
All data stays in the browser. No analytics, no remote calls, no data transmitted anywhere. Local preferences (like resource URL patterns to ignore) are stored with chrome.storage.local, on device only.