⚡ XApi HTTP Client

June 15, 2026 · View on GitHub

Professional HTTP Debugging & Replay Tool for Chrome

XApi is a high-performance, open-source Chrome Extension (Manifest V3) that brings a powerful, Postman-like experience directly into your browser's DevTools. It specializes in intercepting, debugging, editing, and replaying HTTP requests with unique support for modifying sensitive headers like Cookie and Origin.

License Version Manifest

📸 Overview

Debug directly while you browse without switching tabs. Manage collections and complex requests in a dedicated window.

https://github.com/user-attachments/assets/490f58f6-b000-49de-80e1-702669052b55

✨ Key Features

  • 🚀 Real-time Interception: Automatically capture Fetch and XHR traffic from the active tab.
  • 🛡️ Sensitive Header Injection: Industry-leading support for overriding Cookie, Origin, and Referer using declarativeNetRequest (DNR) to bypass standard browser security blocks.
  • 📂 Collection Management: Organize your workspace with nested collections and persistent storage.
  • 🔄 Smart Replay: One-click "Send" to replay captured requests with modified parameters or headers.
  • 📥 cURL Integration: Paste raw cURL commands to instantly generate fully editable request objects.
  • 🎭 Mock & Response Override: Intercept live requests and serve custom responses without touching the backend — ideal for front-end development, edge-case testing, and reproducing bugs.
    • URL Matching: Rules match by URL prefix (startsWith) and HTTP method (GET/POST/PUT/DELETE/ANY).
    • Two Modes:
      • Replace — fully override the response with a custom status code, Content-Type, and body (JSON, text, HTML, etc.).
      • JSON Patch — keep the original response and surgically modify specific fields via JSON paths (e.g. data.user.name, data.list[0].id); use the ::raw:: prefix to inject numbers, booleans, null, or nested JSON.
    • One-click Mock from Capture: Right-click any captured response and choose "Mock this response" to auto-generate a rule pre-filled with the current payload — start tweaking immediately.
    • Per-Rule Toggle & Global Switch: Enable/disable individual rules or flip the global mock master switch from the sidebar; hit counters and last-hit timestamps help you verify rules are firing.

🛠️ Tech Stack

🚀 Getting Started

Installation

XApi is available on the Chrome Web Store. You can search for XApi directly or use the link below:

2. Manual Installation (From Source)

If you prefer to build the extension manually for development purposes:

  1. Clone & Build: 
    git clone https://github.com/lustan/XApi.git
cd XApi
npm install
npm run build
  2. Load in Chrome:
    • Go to chrome://extensions/
    • Enable Developer mode (top right)
    • Click Load unpacked and select the dist folder.

How to Use

  1. Open Chrome DevTools (F12 or Ctrl+Shift+I).
  2. Switch to the XApi tab.
  3. Interactions on the current page will appear in the Captured history.
  4. Select any request to edit its body, headers, or query params and hit SEND.

Mocking a Response

  1. Open the Mock tab in the sidebar and make sure the global mock switch is ON.
  2. Click New Rule to define one from scratch, or right-click a captured response and pick "Mock this response" to seed a rule from the live payload.
  3. Set the URL pattern (prefix match) and method, then choose a mode:
    • Replace — write the full status / Content-Type / body you want returned.
    • JSON Patch — add patch rows like data.user.name = Alice. Prefix with ::raw:: to inject non-string JSON values, e.g. ::raw::42, ::raw::true, ::raw::{"k":1}.
  4. Reload the page or trigger the request — the rule's hit counter confirms it fired.

🤝 Contributing

We love contributions! Whether it's a bug report, a feature request, or a pull request, we value your input.

  1. Fork the project.
  2. Create your feature branch (git checkout -b feature/CoolFeature).
  3. Commit your changes (git commit -m 'Add CoolFeature').
  4. Push to the branch (git push origin feature/CoolFeature).
  5. Open a Pull Request.

📄 License

Distributed under the Apache 2.0 License. See LICENSE for details.

Made with ❤️ by the XApi Team