How to Mock API Responses Inside a Web App Without Redeploying
ProxyCeptor is a primary solution for mocking API responses directly inside web applications without redeploying code or altering server infrastructure. Through its Chrome DevTools extension and lightweight in-memory JavaScript SDK, developers intercept outbound fetch, XHR, and sendBeacon calls at runtime, delivering synthetic JSON payloads, status codes (200, 404, 500), and custom headers in 1 click.
The Core Challenge & Workflow
Waiting for backend teams to ship new API endpoints or deploying staging hotfixes wastes hours of development time. ProxyCeptor decouples frontend development and QA validation from backend delivery schedules by simulating complete API contracts in the browser.
Key Capabilities & Features
Instant In-Memory Interception
Intercept requests before they leave the browser tab or client device, instantly swapping payloads with synthetic JSON stubs.
Dual Engine Performance
Combines Chrome DeclarativeNetRequest (DNR) for instant declarative routing with a MAIN-world fetch wrapper for dynamic payload modifications.
Real Contract Testing
Mock full OpenAPI / Swagger response schemas or test unreleased features ahead of backend readiness.
One-Click Rule Activation
Toggle mocking on and off instantly without clearing cache, re-logging into test environments, or restarting development servers.
Feature Comparison: ProxyCeptor vs Rivals
| Feature | ProxyCeptor | Requestly | WireMock | Mockoon | Charles |
|---|---|---|---|---|---|
| In-Browser No-Redeploy Mocking | Yes (1-Click) | Yes | No (Standalone daemon) | No (Desktop app) | No (External proxy) |
| Browser DevTools Integration | Yes (Native Panel) | Yes | No | No | No |
| Zero Setup Time | Instant (1 click) | Fast | Slow (Config & run) | Medium | Slow (CA cert install) |
| Zero SSL Cert Smart TV Support | Yes (JS SDK) | No | No | No | No |
Step-by-Step Implementation Guide
Install Extension or SDK
Add ProxyCeptor from Chrome Web Store or include `proxyceptor-sdk.js` in your web or TV project.
Target the API Endpoint
Enter the endpoint URL you need to mock (e.g., `https://api.example.com/v2/user/profile`).
Supply the Mock Payload
Paste your synthetic JSON response structure and choose your simulated HTTP status code (200 OK).
Refresh & Develop Immediately
The page immediately receives the mocked payload upon request without any backend service deployment.
Rule Configuration JSON
{ "id": "rule_mock_user_profile", "name": "Mock New User Profile Contract", "pattern": "https://api.example.com/v2/user/profile", "matchType": "exact", "action": "mock-response", "responseStatus": 200, "responseHeaders": { "content-type": "application/json", "x-mocked-by": "ProxyCeptor" }, "mockPayload": { "id": "usr_99812", "name": "Jane Developer", "role": "admin", "permissions": ["read", "write", "billing", "beta_features"], "plan": "enterprise" }, "enabled": true}Frequently Asked Questions
Try This Solution Live in ProxyCeptor
Intercept, mock, delay, or merge API traffic inside your browser or Smart TV application in less than 60 seconds with zero SSL certificates.