aria2 has segmented downloading engine in its core. It can download one file from multiple URLs or multiple connections from one URL. This results in very high speed downloading, very much faster than ordinary browsers. As of 0.3.0 release, It can also download BitTorrent files. As of 0.7.1 release, aria2 supports asynchronous DNS using c-ares or ares. This can improve segmented download performance, especially in Metalink download.
Here are the full list of the feature it supports:
* Command-line interface
* Download files through HTTP/HTTPS/FTP/BitTorrent
* HTTP Proxy support
* FTP through HTTP Proxy
* HTTP BASIC authentication support
* HTTP Proxy authentication support
* Segmented downloading
* Download speed throttling
* Upload speed throttling in BitTorrent
* Cookie support(currently aria2 ignores "expires")
* Run as a daemon process.
* Selective download in multi-file torrent
* BitTorrent Fast extension support
* Metalink version 3.0 support(HTTP/FTP/BitTorrent)