Web Latency Shim

Pause matching Fetch/XHR, CSS, JS, font and image requests using per-tab Chrome debugger controls.

Web Latency Shim helps developers test how webpages behave when selected requests arrive later than expected. Add URL pattern rules with a delay in milliseconds, then explicitly start the request types you want to test in the current tab. The extension pauses eligible Fetch/XHR, stylesheet, script, font, and image requests before they are sent. Each request type has its own per-tab On/Off control. Chrome's debugger continues the original request after the configured wait. You can stop a mode to release pending requests, and view diagnostics showing matched requests and what the extension did. Rules and global effects are saved locally. New rules start disabled, and request modes never start automatically. To test resources loaded at page startup, start the relevant mode and reload the tab. Chrome displays a debugging banner while a mode is active, and DevTools may contend for the same tab. This is a developer testing tool for Chrome 153 or later. The configured delay is a wait before sending an eligible request; it does not throttle bandwidth or slow response streaming. Coverage is limited to eligible HTTP(S) requests in the selected top-level tab. Cached requests, child frames, workers, navigations, and other request types may not be delayed. Static resource modes are experimental.