Modify Response Headers in Angular Proxy (ng serve)

Angular includes the ability to proxy requests to back-end servers. This feature can also be used to modify responses.

To modify responses, create proxy.conf.js in the src folder, then add an entry to modify the response headers:

module.exports = {
	"/path/**": {
		secure: false,
		bypass: function(req, res, opts) {
			res.setHeader("x-your-header", "value");
		}
	}
}

Now, after you run ng server --proxy-config src/proxy.config.js requests to /path will contain the header.

A common application of this approach is to set CORS headers when the Angular dev server is hosting scripts that can be loaded from other applications.

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