What Is API Mocking?
API mocking means replacing a real API response with a controlled fake response, so front-end, QA and integration work can continue without the real backend or with conditions the backend cannot easily produce. Mocks can live in a standalone mock server, in test code, or in a runtime interceptor that rewrites live traffic.
What Is CORS?
CORS (Cross-Origin Resource Sharing) is the browser mechanism that lets a server say which other origins may read its responses. By default JavaScript cannot read a response from a different origin; the server opts in with headers such as Access-Control-Allow-Origin. A "blocked by CORS policy" error means the browser refused to hand the response to your code.
What Is Chrome declarativeNetRequest?
declarativeNetRequest (DNR) is the Chrome extension API, introduced with Manifest V3, that lets an extension block, redirect, upgrade or modify the headers of network requests by registering rules that the browser itself evaluates. The extension never sees the request body, which is good for privacy and speed, but it means DNR cannot change response bodies.
What Is a HAR File?
A HAR (HTTP Archive) file is a JSON document that records every network request a browser made during a session: URLs, methods, headers, cookies, request and response bodies, status codes and timings. Developers and support teams exchange HAR files to reproduce bugs and diagnose slow pages.
What Is an HTTP Interceptor?
An HTTP interceptor is a hook that runs for every HTTP request or response so it can inspect or change it before it continues. The term covers two things: code-level interceptors inside an app (Angular HttpInterceptor, Axios interceptors, a wrapped fetch) and external interceptor tools (browser extensions and proxies) that change traffic without touching the code.
What Is a MITM Proxy?
A man-in-the-middle (MITM) proxy is a proxy that terminates the client's HTTPS connection with its own certificate, reads and optionally changes the decrypted traffic, then opens a separate HTTPS connection to the real server. Debugging tools such as Charles, Fiddler, mitmproxy and Burp Suite work this way, which is why they require installing a trusted root certificate.
What Is a Proxy Interceptor?
A proxy interceptor is a debugging tool that sits between a client (a browser, mobile app or TV app) and the server it talks to, so you can see and change HTTP(S) traffic in real time. It can pause a request, edit its URL, headers or body, return a mocked response, add delay, or drop the call entirely.
What Is SSL Pinning?
SSL pinning (certificate pinning) is a technique where an app accepts only a specific server certificate or public key instead of any certificate signed by a trusted authority. It protects users from interception, but it also blocks debugging proxies such as Charles or Burp, because their generated certificates do not match the pin.
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