aria2 - The ultra fast download utility¶
This program comes with no warranty. You must use this program at your own risk.
aria2 is a utility for downloading files. The supported protocols are HTTP(S), FTP, SFTP, BitTorrent, and Metalink. aria2 can download a file from multiple sources/protocols and tries to utilize your maximum download bandwidth. It supports downloading a file from HTTP(S)/FTP/SFTP and BitTorrent at the same time, while the data downloaded from HTTP(S)/FTP/SFTP is uploaded to the BitTorrent swarm. Using Metalink's chunk checksums, aria2 automatically validates chunks of data while downloading a file like BitTorrent.
The project page is located at https://aria2.github.io/.
Here is a list of features:
Download files through HTTP(S)/FTP/SFTP/BitTorrent
Metalink version 4 (RFC 5854) support(HTTP/FTP/SFTP/BitTorrent)
Metalink version 3.0 support(HTTP/FTP/SFTP/BitTorrent)
Metalink/HTTP (RFC 6249) support
HTTP Proxy support
HTTP BASIC authentication support
HTTP Proxy authentication support
Well-known environment variables for proxy:
HTTP gzip, deflate content encoding support
Verify peer using given trusted CA certificate in HTTPS
Client certificate authentication in HTTPS
Chunked transfer encoding support
Load Cookies from file using the Firefox3 format, Chromium/Google Chrome and the Mozilla/Firefox (1.x/2.x)/Netscape format.
Save Cookies in the Mozilla/Firefox (1.x/2.x)/Netscape format.
Custom HTTP Header support
Persistent Connections support
FTP/SFTP through HTTP Proxy
Download/Upload speed throttling
BitTorrent extensions: Fast extension, DHT, PEX, MSE/PSE, Multi-Tracker, UDP tracker
BitTorrent WEB-Seeding. aria2 requests chunks more than piece size to reduce the request overhead. It also supports pipelined requests with piece size.
BitTorrent Local Peer Discovery
Rename/change the directory structure of BitTorrent downloads completely
JSON-RPC (over HTTP and WebSocket)/XML-RPC interface
Run as a daemon process
Selective download in multi-file torrent/Metalink
Chunk checksum validation in Metalink
Can disable segmented downloading in Metalink
Configuration file support
Download URIs found in a text file or stdin and the destination directory and output file name can be specified optionally
Parameterized URI support
IPv6 support with Happy Eyeballs
Disk cache to reduce disk activity
Versioning and release schedule¶
We use 3 numbers for aria2 version: MAJOR.MINOR.PATCH. We will ship MINOR update on 15th of every month. We may skip a release if we have no changes since the last release. The feature and documentation freeze happens 10 days before the release day (5th day of the month) for translation teams. We will raise an issue about the upcoming release around that day.
We may release PATCH releases between regular releases if we have security issues.
MAJOR version will stay at 1 for the time being.
How to get source code¶
We maintain the source code at Github: https://github.com/aria2/aria2
To get the latest source code, run following command:
$ git clone https://github.com/aria2/aria2.git
This will create aria2 directory in your current directory and source files are stored there.
OSX or GnuTLS or OpenSSL or Windows
None. Optional: libnettle+libgmp or libgcrypt or OpenSSL (see note)
libxml2 or Expat.
None. Optional: OSX or libnettle or libgcrypt or OpenSSL or Windows (see note)
gzip, deflate in HTTP
libxml2 or Expat.
JSON-RPC over WebSocket
libnettle or libgcrypt or OpenSSL
libxml2 has precedence over Expat if both libraries are installed.
If you prefer Expat, run configure with
On Apple OSX the OS-level SSL/TLS support will be preferred. Hence
neither GnuTLS nor OpenSSL are required on that platform. If you'd
like to disable this behavior, run configure with
GnuTLS has precedence over OpenSSL if both libraries are installed.
If you prefer OpenSSL, run configure with
On Windows there is SSL implementation available that is based on
the native Windows SSL capabilities (Schannel) and it will be
preferred. Hence neither GnuTLS nor OpenSSL are required on that
platform. If you'd like to disable this behavior, run configure
On Apple OSX the OS-level checksum support will be preferred,
unless aria2 is configured with
libnettle has precedence over libgcrypt if both libraries are
installed. If you prefer libgcrypt, run configure with
--without-libnettle --with-libgcrypt. If OpenSSL is selected over
GnuTLS, neither libnettle nor libgcrypt will be used.
If none of the optional dependencies are installed, an internal implementation that only supports md5 and sha1 will be used.
On Windows there is SSL implementation available that is based on
the native Windows capabilities and it will be preferred, unless
aria2 is configured with
A user can have one of the following configurations for SSL and crypto libraries:
GnuTLS + libgcrypt
GnuTLS + libnettle
Apple TLS (OSX only)
Windows TLS (Windows only)
You can disable BitTorrent and Metalink support by providing
--disable-metalink to the configure
In order to enable async DNS support, you need c-ares.
How to build¶
aria2 is primarily written in C++. Initially it was written based on
C++98/C++03 standard features. We are now migrating aria2 to C++11
standard. The current source code requires C++11 aware compiler. For
well-known compilers, such as g++ and clang, the
-std=c++0x flag must be supported.
In order to build aria2 from the source package, you need following development packages (package name may vary depending on the distribution you use):
libgnutls-dev (Required for HTTPS, BitTorrent, Checksum support)
nettle-dev (Required for BitTorrent, Checksum support)
libgmp-dev (Required for BitTorrent)
libssh2-1-dev (Required for SFTP support)
libc-ares-dev (Required for async DNS support)
libxml2-dev (Required for Metalink support)
zlib1g-dev (Required for gzip, deflate decoding support in HTTP)
libsqlite3-dev (Required for Firefox3/Chromium cookie support)
pkg-config (Required to detect installed libraries)
You can use libgcrypt-dev instead of nettle-dev and libgmp-dev:
libgpg-error-dev (Required for BitTorrent, Checksum support)
libgcrypt-dev (Required for BitTorrent, Checksum support)
You can use libssl-dev instead of libgnutls-dev, nettle-dev, libgmp-dev, libgpg-error-dev and libgcrypt-dev:
libssl-dev (Required for HTTPS, BitTorrent, Checksum support)
You can use libexpat1-dev instead of libxml2-dev:
libexpat1-dev (Required for Metalink support)
On Fedora you need the following packages: gcc, gcc-c++, kernel-devel, libgcrypt-devel, libxml2-devel, openssl-devel, gettext-devel, cppunit
If you downloaded source code from git repository, you have to install following packages to get autoconf macros:
And run following command to generate configure script and other files necessary to build the program:
$ autoreconf -i
Also you need Sphinx to build man page.
If you are building aria2 for Mac OS X, take a look at the makerelease-osx.mk GNU Make makefile.
The quickest way to build aria2 is first run configure script:
To build statically linked aria2, use
$ ./configure ARIA2_STATIC=yes
After configuration is done, run
make to compile the program:
The configure script checks available libraries and enables as many features as possible except for experimental features not enabled by default.
Since 1.1.0, aria2 checks the certificate of HTTPS servers by default.
If you build with OpenSSL or the recent version of GnuTLS which has
gnutls_certificate_set_x509_system_trust() function and the
library is properly configured to locate the system-wide CA
certificates store, aria2 will automatically load those certificates
at the startup. If it is not the case, I recommend to supply the path
to the CA bundle file. For example, in Debian the path to CA bundle
file is '/etc/ssl/certs/ca-certificates.crt' (in ca-certificates
package). This may vary depending on your distribution. You can give
it to configure script using
$ ./configure --with-ca-bundle='/etc/ssl/certs/ca-certificates.crt' $ make
--with-ca-bundle option, you will encounter the error when
accessing HTTPS servers because the certificate cannot be verified
without CA bundle. In such case, you can specify the CA bundle file
--ca-certificate option. If you don't have CA bundle
file installed, then the last resort is disable the certificate
Using the native OSX (AppleTLS) and/or Windows (WinTLS) implementation
will automatically use the system certificate store, so
--with-ca-bundle is not necessary and will be ignored when using
By default, the bash_completion file named
aria2c is installed to
$prefix/share/doc/aria2/bash_completion. To change
the install directory of the file, use
make the executable is located at
aria2 uses CppUnit for automated unit testing. To run the unit test:
$ make check
Cross-compiling Windows binary¶
In this section, we describe how to build a Windows binary using a mingw-w64 (http://mingw-w64.org/doku.php) cross-compiler on Debian Linux. The MinGW (http://www.mingw.org/) may not be able to build aria2.
The easiest way to build Windows binary is use Dockerfile.mingw. See Dockerfile.mingw how to build binary. If you cannot use Dockerfile, then continue to read following paragraphs.
Basically, after compiling and installing depended libraries, you can
do cross-compile just passing appropriate
--host option and
variables to configure. For convenience and lowering our own
development cost, we provide easier way to configure the build
mingw-config script is a configure script wrapper for mingw-w64.
We use it to create official Windows build. This script assumes
following libraries have been built for cross-compile:
Some environment variables can be adjusted to change build settings:
cross-compile to build programs to run on
HOST. It defaults to
i686-w64-mingw32. To build 64bit binary, specify
Prefix to the directory where dependent libraries are installed. It defaults to
-I$PREFIX/includewill be added to
-L$PREFIX/libwill be added to
$PREFIX/lib/pkgconfigwill be set to
For example, to build 64bit binary do this:
$ HOST=x86_64-w64-mingw32 ./mingw-config
If you want libaria2 dll with
--enable-libaria2, then don't use
ARIA2_STATIC=yes and prepare the DLL version of external
Cross-compiling Android binary¶
In this section, we describe how to build Android binary using Android NDK cross-compiler on Debian Linux.
At the time of this writing, Android NDK r21e should compile aria2 without errors.
android-config script is a configure script wrapper for Android
build. We use it to create official Android build. This script
assumes the following libraries have been built for cross-compile:
When building the above libraries, make sure that disable shared library and enable only static library. We are going to link those libraries statically.
android-config assumes that
environment variables are defined.
We currently use Android NDK r21e.
$NDK should point to the
directory to Anroid NDK. The build tools will be found under
All the dependent libraries must be installed under
make to compile sources.
Sphinx is used to build the
documentation. aria2 man pages will be build when you run
they are not up-to-date. You can also build HTML version of aria2 man
make html. The HTML version manual is also available at
About file names¶
The file name of the downloaded file is determined as follows:
- single-file mode
If "name" key is present in .torrent file, file name is the value of "name" key. Otherwise, file name is the base name of .torrent file appended by ".file". For example, .torrent file is "test.torrent", then file name is "test.torrent.file". The directory to store the downloaded file can be specified by -d option.
- multi-file mode
The complete directory/file structure mentioned in .torrent file is created. The directory to store the top directory of downloaded files can be specified by -d option.
Before download starts, a complete directory structure is created if
needed. By default, aria2 opens at most 100 files mentioned in
.torrent file, and directly writes to and reads from these files.
The number of files to open simultaneously can be controlled by
aria2 supports mainline compatible DHT. By default, the routing table
for IPv4 DHT is saved to
$XDG_CACHE_HOME/aria2/dht.dat and the
routing table for IPv6 DHT is saved to
$XDG_CACHE_HOME/aria2/dht6.dat unless files exist at
$HOME/.aria2/dht6.dat. aria2 uses same
port number to listen on for both IPv4 and IPv6 DHT.
UDP tracker support is enabled when IPv4 DHT is enabled. The port
number of UDP tracker is shared with DHT. Use
option to change the port number.
Other things should be noted¶
-ooption is used to change the file name of .torrent file itself, not a file name of a file in .torrent file. For this purpose, use
The port numbers that aria2 uses by default are 6881-6999 for TCP and UDP.
aria2 doesn't configure port-forwarding automatically. Please configure your router or firewall manually.
The maximum number of peers is 55. This limit may be exceeded when download rate is low. This download rate can be adjusted using
As of release 0.10.0, aria2 stops sending request message after selective download completes.
netrc support is enabled by default for HTTP(S)/FTP/SFTP. To disable netrc support, specify -n command-line option. Your .netrc file should have correct permissions(600).
The WebSocket server embedded in aria2 implements the specification defined in RFC 6455. The supported protocol version is 13.
The libaria2 is a C++ library which offers aria2 functionality to the
client code. Currently, libaria2 is not built by default. To enable
--enable-libaria2 configure option. By default,
only the shared library is built. To build static library, use
--enable-static configure option as well. See libaria2
documentation to know how to use API.