Architecture & EngineDual Engine• 6 min read
How ProxyCeptor Intercepts fetch, XHR, and sendBeacon Calls
Summary: A deep-dive into how ProxyCeptor combines Chrome declarativeNetRequest (DNR) with in-page JavaScript interception to modify traffic without breaking pages.
Why This Rule Matters for Developers & QA
Understanding how network interceptors operate helps developers diagnose complex race conditions and write safer integration tests.
Step-by-Step Implementation Guide
1
Declarative Net Request (DNR) Layer
Browser-level filtering executes URL redirects and header modifications before requests leave the network socket.
2
In-Page Fetch & XHR Interceptor
Injected into the page MAIN world to capture and mutate request/response bodies that DNR cannot inspect.
3
Fail-Safe Fallback Protection
If a custom transform throws an error, ProxyCeptor automatically falls back to original traffic to ensure zero broken pages.
Configuration Snippet
How ProxyCeptor Intercepts fetch, XHR, and sendBeacon Calls — proxyceptor-rule.json
JSON
// Concept: ProxyCeptor Hybrid Interception Pipeline[ App Code ] │ ▼ (fetch / XHR / sendBeacon)[ MAIN World Interceptor ] ── (Body Mock / Deep Merge / Delay) │ ▼[ Chrome DNR Engine ] ─────── (URL Rewrite / Header Injection / Block) │ ▼[ Remote Server / CDN ]