aria2 - The ultra fast download utility

aria2 is a lightweight multi-protocol & multi-source, cross platform download utility operated in command-line. It supports HTTP/HTTPS, FTP, SFTP, BitTorrent and Metalink.
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By aria2

cpp11 http download rpc ftp bittorrent sftp metalink

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

See aria2 Online Manual
(Russian translation
, Portuguese
translation <>
_) to learn
how to use aria2.


Here is a list of features:

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:

To get the latest source code, run following command::

$ git clone

This will create aria2 directory in your current directory and source
files are stored there.


======================== ========================================
features dependency
======================== ========================================
HTTPS OSX or GnuTLS or OpenSSL or Windows
SFTP libssh2
BitTorrent None. Optional: libnettle+libgmp or libgcrypt
or OpenSSL (see note)
Metalink libxml2 or Expat.
Checksum None. Optional: OSX or libnettle or libgcrypt
or OpenSSL or Windows (see note)
gzip, deflate in HTTP zlib
Async DNS C-Ares
Firefox3/Chromium cookie libsqlite3
XML-RPC libxml2 or Expat.
JSON-RPC over WebSocket libnettle or libgcrypt or OpenSSL
======================== ========================================

.. note::

libxml2 has precedence over Expat if both libraries are installed.
If you prefer Expat, run configure with --without-libxml2.

.. note::

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 --without-gnutls

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
with --without-wintls.

.. note::

On Apple OSX the OS-level checksum support will be preferred,
unless aria2 is configured with --without-appletls.

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 --without-wintls.

A user can have one of the following configurations for SSL and crypto

You can disable BitTorrent and Metalink support by providing
--disable-bittorrent and --disable-metalink to the configure
script respectively.

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++11 or
-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):

You can use libgcrypt-dev instead of nettle-dev and libgmp-dev:

You can use libssl-dev instead of
libgnutls-dev, nettle-dev, libgmp-dev, libgpg-error-dev and libgcrypt-dev:

You can use libexpat1-dev instead of libxml2-dev:

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 GNU Make makefile.

The quickest way to build aria2 is first run configure script::

$ ./configure

To build statically linked aria2, use ARIA2_STATIC=yes
command-line option::

$ ./configure ARIA2_STATIC=yes

After configuration is done, run make to compile the program::

$ make

See Cross-compiling Windows binary to create a Windows binary.
See Cross-compiling Android binary
to create an Android binary.

The configure script checks available libraries and enables as many
features as possible except for experimental features not enabled by

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 --with-ca-bundle option::

$ ./configure --with-ca-bundle='/etc/ssl/certs/ca-certificates.crt'
$ make

Without --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
using aria2's --ca-certificate option. If you don't have CA bundle
file installed, then the last resort is disable the certificate
validation using --check-certificate=false.

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
these implementations.

By default, the bash_completion file named aria2c is installed to
the directory $prefix/share/doc/aria2/bash_completion. To change
the install directory of the file, use --with-bashcompletiondir

After a make the executable is located at src/aria2c.

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 ( cross-compiler on Debian
Linux. The MinGW ( may not be able to build

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 /usr/local/$HOST. -I$PREFIX/include will be
added to CPPFLAGS. -L$PREFIX/lib will be added to
LDFLAGS. $PREFIX/lib/pkgconfig will 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 $ANDROID_HOME and $NDK
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

After android-config, run make to compile sources.

Building documentation

Sphinx <> is used to build the
documentation. aria2 man pages will be build when you run make if
they are not up-to-date. You can also build HTML version of aria2 man
page by make html. The HTML version manual is also available at
online <>
translation <>
, Portuguese
translation <>


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

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
--bt-max-open-files option.


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/dht.dat or $HOME/.aria2/dht6.dat. aria2 uses same
port number to listen on for both IPv4 and IPv6 DHT.

UDP tracker

UDP tracker support is enabled when IPv4 DHT is enabled. The port
number of UDP tracker is shared with DHT. Use --dht-listen-port
option to change the port number.

Other things should be noted


The current implementation supports HTTP(S)/FTP/SFTP/BitTorrent. The
other P2P protocols are ignored. Both Metalink4 (RFC 5854) and
Metalink version 3.0 documents are supported.

For checksum verification, md5, sha-1, sha-224, sha-256, sha-384 and
sha-512 are supported. If multiple hash algorithms are provided, aria2
uses stronger one. If whole file checksum verification fails, aria2
doesn't retry the download and just exits with non-zero return code.

The supported user preferences are version, language, location,
protocol and os.

If chunk checksums are provided in Metalink file, aria2 automatically
validates chunks of data during download. This behavior can be turned
off by a command-line option.

If signature is included in a Metalink file, aria2 saves it as a file
after the completion of the download. The file name is download
file name + ".sig". If same file already exists, the signature file is
not saved.

In Metalink4, multi-file torrent could appear in metalink:metaurl
element. Since aria2 cannot download 2 same torrents at the same
time, aria2 groups files in metalink:file element which has same
BitTorrent metaurl and downloads them from a single BitTorrent swarm.
This is basically multi-file torrent download with file selection, so
the adjacent files which is not in Metalink document but shares same
piece with selected file are also created.

If relative URI is specified in metalink:url or metalink:metaurl
element, aria2 uses the URI of Metalink file as base URI to resolve
the relative URI. If relative URI is found in Metalink file which is
read from local disk, aria2 uses the value of --metalink-base-uri
option as base URI. If this option is not specified, the relative URI
will be ignored.


The current implementation only uses rel=duplicate links only. aria2
understands Digest header fields and check whether it matches the
digest value from other sources. If it differs, drop connection.
aria2 also uses this digest value to perform checksum verification
after download finished. aria2 recognizes geo value. To tell aria2
which location you prefer, you can use --metalink-location option.


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
libaria2, use --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.