# Mock Express

> Mock Express lets developers intercept and modify HTTP requests in the browser. Mock API responses, block or delay requests, redirect URLs, and more—all with a simple interface. Ideal for frontend devs and QA testing dynamic API behavior.

Canonical page: [https://chrome-stats.com/d/mock-express](https://chrome-stats.com/d/mock-express)

## Overview

- **ID:** `mock-express`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Mock Express
- **Category:** web-development
- **Daily users:** 60
- **Weekly downloads:** 4
- **Version:** 2.0.5
- **Last updated:** 2026-03-19
- **First published:** 2025-07-27
- **Size:** 757 KB
- **Data as of:** 2026-09-07
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/mock-express/)
- **Website:** [https://www.mockexpress.com/](https://www.mockexpress.com/)

## Description

MockExpress is a powerful browser extension designed for developers and testers to intercept, inspect, and modify HTTP requests and responses—all directly from the browser. Whether you're working with unstable APIs, simulating edge cases, or testing UI behavior under different backend conditions, MockExpress gives you the tools you need.

🚀 Key Features
🔧 Request Actions
Modify Request
Alter headers, body content, or URL of outgoing API requests before they’re sent.

Block Request
Instantly stop specific API calls from being made—useful for testing error states or eliminating unwanted traffic.

Delay Request
Simulate slow networks by delaying requests for a custom duration to mimic latency or throttling.

🔁 Response Actions
Mock / Modify Response
Override real API responses with custom JSON, status codes, or error messages. Ideal for testing frontend components without needing real backend responses.

🌐 URL Actions
URL Redirect
Seamlessly reroute API requests to different endpoints or servers (e.g., from production to staging).

Modify Query Parameters
Add, remove, or change query parameters in outgoing requests dynamically.

🔍 Coming Soon
Real-Time Request Monitoring & Logging
View and track outgoing requests, intercepted actions, and responses in real time for debugging and validation.

GraphQL Request Mocking
Full support for intercepting, modifying, and mocking GraphQL queries and mutations.

Rules Export / Import
Save and share your rule configurations easily across teams or environments.

Advanced Filtering
Apply conditions to rules based on method, hostname, or request path with more precision.

👨‍💻 Built For
Frontend Developers
Easily test UI components against various API states—without waiting for backend readiness.

QA Engineers
Simulate edge cases like timeouts, server errors, and malformed responses without altering production systems.

Dev Teams
Create stable test environments, even when backend services are unstable, incomplete, or unavailable.

🔒 Privacy & Security
MockExpress runs entirely within your browser environment. It does not send or store any data externally. Your mock rules, request logs, and configurations are all stored locally using browser storage (no servers, no tracking, no analytics).

✅ Why Choose MockExpress?
No backend or network setup needed

Intuitive interface with clear rule management

Lightweight and fast—optimized for developer workflows

Works seamlessly across most modern frontend stacks (React, Angular, Vue, etc.)

🧩 Integration & Compatibility
Compatible with most modern frontend frameworks

## Rankings

- #14,870 — Overall
- #8 — mock
- #16 — ali express
- #40 — press
- #118 — response
- #121 — component

## Permissions and access

### Permissions

- `storage`
- `unlimitedStorage`
- `contextMenus`
- `<all_urls>`

### Content script matches

- `<all_urls>`

## Safety

- **Risk impact:** Moderate risk impact
- **Risk likelihood:** Moderate risk likelihood

### Analysis details

- Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- This extension has low user count. Unpopular extensions may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

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Source: [Chrome-Stats](https://chrome-stats.com/d/mock-express)