Modify Headers

A Chrome extension that allows users to add, modify, and delete HTTP request headers for specific websites with profile management.

Features

• Profile Management: Create multiple profiles, each targeting specific websites
• Header Modification: Add, modify, or delete HTTP headers
• Toggle Profiles: Enable/disable profiles individually
• URL Pattern Matching: Flexible URL pattern matching for targeting specific sites
• Privacy-Focused: Uses Manifest V3 and declarativeNetRequest API

Installation

1. Open Chrome and navigate to chrome://extensions/
2. Enable "Developer mode" in the top right corner
3. Click "Load unpacked"
4. Select the modify-header folder
5. The extension icon should appear in your toolbar

Usage

Creating a Profile

1. Click the extension icon in the toolbar
2. Click "New Profile"
3. Enter a profile name (e.g., "Development API")
4. Enter a URL pattern:
   • example.com - matches any URL containing example.com
   • *.example.com - matches all subdomains of example.com
   • https://api.example.com/* - matches all URLs starting with this
5. Add headers:
   • Add: Add a new header to requests
   • Modify: Change an existing header value
   • Delete: Remove a header from requests
6. Click "Save"

Managing Profiles

• Enable/Disable: Use the toggle switch on each profile
• Edit: Click the "Edit" button to modify a profile
• Delete: Click the "Delete" button to remove a profile

Example Use Cases

Development Environment

Profile: Dev API Headers URL Pattern: localhost:3000 Headers:

• Add: X-Debug-Mode = true
• Add: Authorization = Bearer dev-token-123

API Testing

Profile: Custom API Headers URL Pattern: https://api.example.com/* Headers:

• Add: X-API-Key = your-api-key
• Modify: User-Agent = CustomBot/1.0
• Delete: Referer

CORS Testing

Profile: CORS Headers URL Pattern: example.com Headers:

• Add: Origin = https://example.com
• Add: Access-Control-Request-Method = POST

File Structure

/modify-header
├── manifest.json          # Extension configuration
├── background.js          # Service worker for managing rules
├── popup.html             # Extension popup UI
├── popup.css              # Popup styling
├── popup.js               # Popup logic and interactions
├── README.md              # This file
└── icons/
    ├── icon16.png         # 16x16 icon
    ├── icon48.png         # 48x48 icon
    └── icon128.png        # 128x128 icon

Technical Details

Permissions

• declarativeNetRequest: For modifying HTTP headers
• declarativeNetRequestWithHostAccess: For host-specific modifications
• storage: For saving user profiles
• <all_urls>: For applying rules to any website

Storage

Profiles are stored in chrome.storage.local with the following structure:

{
	profiles: [
		{
			id: "unique-id",
			name: "Profile Name",
			urlPattern: "example.com",
			enabled: true,
			headers: [
				{
					action: "add", // "add", "modify", or "delete"
					name: "X-Custom-Header",
					value: "custom-value",
				},
			],
			createdAt: 1234567890,
		},
	];
}

URL Pattern Matching

The extension converts user-friendly URL patterns to declarativeNetRequest URL filters:

• example.com → *://*.example.com/*
• https://api.example.com → https://api.example.com*
• *.example.com → Used as-is
• Wildcards (*) are supported

Limitations

• Maximum of 5000 dynamic rules (Chrome limitation)
• Header modifications apply to the main document and all resource types
• Some headers cannot be modified due to browser security restrictions (e.g., Host, Cookie in some contexts)

Troubleshooting

Extension not working?

1. Check if the profile is enabled (toggle switch should be green)
2. Verify the URL pattern matches the target website
3. Open Chrome DevTools > Network tab to inspect headers
4. Check the extension's service worker logs:
   • Go to chrome://extensions/
   • Click "service worker" under Modify Headers
   • Look for errors in the console

Headers not being applied?

1. Some headers are protected by the browser and cannot be modified
2. Ensure the URL pattern correctly matches the target URL
3. Try using a more specific URL pattern
4. Disable other extensions that might interfere with headers

Profile changes not taking effect?

• Changes are applied immediately when you save a profile
• If issues persist, try:
  1. Disable and re-enable the profile
  2. Reload the extension from chrome://extensions/
  3. Restart Chrome

Development

Modifying the Extension

1. Make changes to the source files
2. Go to chrome://extensions/
3. Click the reload icon for Modify Headers
4. Test your changes

Debugging

• Background Script: Click "service worker" in chrome://extensions/
• Popup: Right-click the popup and select "Inspect"
• Storage: Use Chrome DevTools > Application > Storage > Local Storage

Privacy

This extension:

• Does NOT collect any data
• Does NOT send data to external servers
• Stores all data locally in your browser
• Only modifies headers for websites matching your URL patterns

License

This project is provided as-is for educational and development purposes.

Support

For issues or questions:

1. Check the Troubleshooting section above
2. Review Chrome's declarativeNetRequest API documentation
3. Inspect the browser console for error messages

Version History

v1.0 (Current)

• Profile management with enable/disable
• Import / Export / Clone Profiles
• Add, modify, and delete headers
• URL pattern matching
• Manifest V3 compatibility