Open Radar

 
Summary:
NSMutableURLRequest allow setting the user-agent by adding a string value for HTTP header field "User-Agent" however, there is no way to incorporate the default user-agent.

Steps to Reproduce:
Create a NSURLRequest for a HTTP download without changing anything and the server will see a user-agent like:

MyApplicationName/1.0 CFNetwork/720.3.13 Darwin/14.3.0 (x86_64)

where MyApplicationName and 1.0 come from the executable name and the CFBundleVersion. The CFNetwork and Darwin versioning is coming from the system.

If in the code you set the User-Agent for the URL request using:

NSMutableURLRequest* downloadRequest = [[[NSMutableURLRequest alloc] initWithURL:url]
                                autorelease];

[downloadRequest addValue:@"My Custom User Agent/1.0" forHTTPHeaderField:@"User-Agent"];

then the user agent is just "My Custom User Agent/1.0" and the CFNetwork and Darwin versions are not appended. 

When using WebKit you can build a custom user agent by using the WebView method

- (void)setCustomUserAgent:(NSString *)userAgentString;

where the existing user agent string can be appending by first calling: 

- (NSString *)userAgentForURL:(NSURL *)URL;

There doesn't appear to be any way to get the default user-agent string by using any method in NSURLRequest

Version:
Tested on OS X 10.10.3 (14D136)