aria2 is a lightweight multi-protocol & multi-source command-line download utility. It supports HTTP/HTTPS, FTP, BitTorrent and Metalink. aria2 can be manipulated via built-in JSON-RPC and XML-RPC interfaces.
aria2 can download a file from multiple sources/protocols and tries to utilize your maximum download bandwidth. Really speeds up your download experience.
aria2 doesn't require much memory and CPU time. The physical memory usage is typically 4MiB (normal HTTP/FTP downloads) to 9MiB (BitTorrent downloads). CPU usage in BitTorrent with download speed of 2.8MiB/sec is around 6%.
All features you want in BitTorrent client are available: DHT, PEX, Encryption, Magnet URI, Web-Seeding, Selective Downloads and Local Peer Discovery.
aria2 supports The Metalink Download Description Format(aka Metalink v4) and Metalink/HTTP. Old Metalink v3 is also supported. Metalink offers File verification, HTTP/FTP/BitTorrent integration and Configuration for language, location, OS, etc.
aria2 supports RPC interface to control the aria2 process. The supported interfaces are JSON-RPC (over HTTP and WebSocket) and XML-RPC.
Command-line scares you off? No, aria2 is really easy to use!!
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.