ASIHTTPRequest is an easy to use wrapper around the CFNetwork API that makes some of the more tedious aspects of communicating with web servers easier. It is written in Objective-C and works in both Mac OS X and iPhone applications.

It is suitable performing basic HTTP requests and interacting with REST-based services (GET / POST / PUT / DELETE). The included ASIFormDataRequest subclass makes it easy to submit POST data and files using multipart/form-data.

It provides:

• A straightforward interface for submitting data to and fetching data from webservers
• Download data to memory or directly to a file on disk
• Submit files on local drives as part of POST data, compatible with the HTML file input mechanism
• Stream request bodies directly from disk to the server, to conserve memory
• Resume for partial downloads
• Easy access to request and response HTTP headers
• Progress delegates (NSProgressIndicators and UIProgressViews) to show information about download AND upload progress
• Auto-magic management of upload and download progress indicators for operation queues
• Basic, Digest + NTLM authentication support, credentials are automatically re-used for the duration of a session, and can be stored for later in the Keychain.
• Cookie support
• [NEW] Requests can continue to run when your app moves to the background (iOS 4+)
• GZIP support for response data AND request bodies
• The included ASIDownloadCache class lets requests transparently cache responses, and allow requests for cached data to succeed even when there is no network available
• [NEW] ASIWebPageRequest – download complete webpages, including external resources like images and stylesheets. Pages of any size can be indefinitely cached, and displayed in a UIWebview / WebView even when you have no network connection.
• Easy to use support for Amazon S3 – no need to fiddle around signing requests yourself!
• Full support for Rackspace Cloud Files
• [NEW] Client certificates support
• Supports manual and auto-detected proxies, authenticating proxies, and PAC file auto-configuration. The built-in login dialog lets your iPhone application work transparently with authenticating proxies without any additional effort.
• Bandwidth throttling support
• Support for persistent connections
• Supports synchronous & asynchronous requests
• Get notifications about changes in your request state via delegation or [NEW] blocks (Mac OS X 10.6, iOS 4 and above)
• Comes with a broad range of unit tests

ASIHTTPRequest is compatible with Mac OS 10.5 or later, and iOS 3.0 or later.

Documentation is available here.