Web Sniffer

Monitor, filter, and validate analytics network payloads in Chrome DevTools

Detailed description Web Sniffer is a Chrome DevTools panel built for analytics engineers, QA, and developers who need to see exactly what their site sends to Segment, GA4, Amplitude, Mixpanel, Adobe, and other vendors. What you can do Capture analytics requests — Filter by URL pattern and vendor preset. See method, status, event count, and decoded JSON for every matching request. Search & filter events — Build filters from the JSON tree (right-click → Add to Filters). Export HAR or event JSON. Validate flows — Upload ESS Excel or JSON test suites. Web Sniffer replays browser steps and reports pass/fail for expected events. Spec Sheet — Import/export Generic ESS workbooks for config, expected events, test steps, and filter presets. Header & redirect rules — Set/remove headers or redirect matching URLs to mock responses (declarativeNetRequest). Collections — Save capture snapshots, replay them later, and compare side-by-side against your current session. Replay requests — Re-fire a captured request in the inspected page context with one click. Pro features (sign-in required) Validate, Spec Sheet, Rules, Collections, and exports require a free account during the launch promo. Pro is $39/year after the trial period. Privacy Network capture data stays local in DevTools. We do not sell data. See our privacy policy for details.