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Mockttp
What it is
Mockttp is an open-source JavaScript library for intercepting, changing, and testing HTTP requests and responses. It supports integration tests in Node.js and browsers, including transparent proxying and HTTPS, and can also form the basis of a custom proxy to capture, inspect, or rewrite traffic. Its tools can stub responses, verify requests, generate self-signed certificates for HTTPS mocking, and mock traffic inside or outside the process. For parallel tests, Mockttp can configure ports, mock URLs, and proxy settings automatically. It works with promise-capable testing tools and HTTP clients; Mocha, Chai, and Superagent are optional examples. Browser testing requires an admin server started outside the browser, since browsers cannot start an HTTP server or proxy themselves. The library is free and available for Linux, macOS, Windows, web, and self-hosted use. The setup guidance cautions against trusting a test certificate authority system-wide or sharing its private key, since either could let an attacker impersonate secure connections.
For and against
For
- Supports HTTP tests in Node.js and browsers.
- Can mock HTTPS with generated self-signed certificates.
- Parallel tests can use automatically configured ports and proxy settings.
- Works with promise-capable testing tools and HTTP clients.
- Open-source and free.
Against
- Browser tests require an admin server outside the browser.
- The setup guide warns against system-wide trust of test certificates.
- Sharing a test certificate authority's private key can put secure connections at risk.
The verdict
Mockttp provides flexible HTTP mocking and proxy capabilities for JavaScript testing, including HTTPS and parallel test support. Browser tests need an external admin server, and certificate handling requires care.
Who it suits
Mockttp suits JavaScript developers who need HTTP mocking, proxying, or integration testing in Node.js or browsers. It can also help teams building custom tools to inspect or rewrite HTTP traffic.
Plans and prices
Hobbyist
basic traffic viewing and rewriting · manual breakpoints · built-in HTTP client
Read 4 Oct 2026 · httptoolkit.com
Professional
automated mocking and rewriting · import/export · advanced debugging and configuration
Read 4 Oct 2026 · httptoolkit.com
Team
team licensing · centralized billing · team workspaces coming soon · additional options on request
Read 4 Oct 2026 · httptoolkit.com
On the record
- Browser setup
- Browser tests require an admin server started outside the browser because browsers cannot start an HTTP server or proxy themselves.github.com · read 4 Oct 2026
- Commercial product distinction
- HTTP Toolkit lists automated HTTP mocking and rewriting among Professional plan features, while Mockttp itself is published as a JavaScript library in a public GitHub repository.httptoolkit.com · read 4 Oct 2026
- Desktop platforms
- HTTP Toolkit provides installation packages for Windows, Mac, and Linux.httptoolkit.com · read 4 Oct 2026
- HTTPS certificate caution
- The setup guide warns against trusting a test CA system-wide or sharing its private key, because doing so could let an attacker impersonate secure connections.github.com · read 4 Oct 2026
- HTTP Toolkit privacy
- HTTP Toolkit says HTTP request and response contents are never collected and are stored only locally on the user’s machine.httptoolkit.com · read 4 Oct 2026
- Integrations
- The README example uses Mocha, Chai, and Superagent, while noting that these tools are optional and Mockttp can work with other promise-capable testing tools and HTTP clients.github.com · read 4 Oct 2026
- Maker and location
- The HTTP Toolkit privacy policy identifies Toolshed Labs SLU as the operator and gives its address in Barcelona, Spain.httptoolkit.com · read 4 Oct 2026
- Mocking features
- The library can stub responses, verify requests, mock HTTPS with generated self-signed certificates, and mock traffic inside or outside its process.github.com · read 4 Oct 2026
- Parallel testing
- Mockttp supports parallel mocking with automatically configured ports, mock URLs, and proxy settings.github.com · read 4 Oct 2026
- Proxy use
- Mockttp can be used to build custom HTTP proxies that capture, inspect, or rewrite traffic.github.com · read 4 Oct 2026
- Security support
- The latest published Mockttp version is actively supported, and the preceding major version receives security fixes for six months after the next major release.github.com · read 4 Oct 2026
- Testing use
- Mockttp supports HTTP integration tests that can run in Node.js and browsers, including transparent proxying and HTTPS.github.com · read 4 Oct 2026
- Vulnerability reporting
- Mockttp vulnerabilities can be reported through GitHub’s private security reporting channels, and confirmed vulnerabilities are to be fixed and published as advisories within 90 days.github.com · read 4 Oct 2026
- What Mockttp does
- Mockttp intercepts, transforms, or tests HTTP requests and responses in JavaScript.github.com · read 4 Oct 2026
