Can aria2 be built from source code?

Yes, aria2 can be compiled and built directly from its source code, provided that your system has a compatible C++ compiler and the necessary development libraries installed. Building from source allows you to customize features, optimize the binary for your specific hardware architecture, and use the absolute latest updates or patches from the official codebase. To successfully compile the utility, you must first satisfy several mandatory build tools and fundamental dependencies, alongside choosing optional libraries depending on the protocols and cryptographic backends you want enabled.

Mandatory Build Tools and Core Dependencies

Before compiling aria2, your system environment needs basic development tools capable of handling the configuration and build process:

• C++ Compiler: A compiler supporting at least the C++11 standard, such as GCC (g++) 4.8.3 or later, or Clang.
• Build Automation Tools: make and pkg-config are required to manage compilation scripts and locate package dependencies.
• Libxml2 or Expat: At least one of these XML parsing libraries is strictly mandatory because aria2 relies on them to parse Metalink files.

Cryptographic and SSL Dependencies

aria2 requires a cryptographic library to handle HTTPS, SFTP, and BitTorrent transfers securely. You must install at least one of the following backends:

• OpenSSL: The most common backend used on Linux systems.
• GnuTLS: A viable alternative to OpenSSL.
• CyaSSL/WolfSSL: Often selected for low-resource or embedded environments.
• Apple TLS / Windows TLS: Native security frameworks can also be utilized if building on macOS or Windows.

Optional Feature Dependencies

Depending on the specific protocols and optimizations you require, you can include several optional packages before running the build configuration:

• libssh2: Required explicitly if you need support for the SFTP protocol.
• Ancillary Compression Libraries: zlib and libsqlite3 are highly recommended; zlib handles GZip deflation for faster HTTP downloads, while libsqlite3 is utilized to save and restore your persistent download history.
• C-Ares: An asynchronous DNS resolution library that significantly speeds up multi-connection downloads by resolving domain names in parallel.