# aria2 — Lightweight Multi-Protocol Download Utility

> aria2 is a lightweight multi-protocol and multi-source command-line download utility supporting HTTP/HTTPS, FTP, SFTP, BitTorrent, and Metalink with minimal resource usage.

## Install

Save as a script file and run:

# aria2 — Lightweight Multi-Protocol Download Utility

## Quick Use
```bash
# Install
sudo apt install aria2   # Debian/Ubuntu
brew install aria2       # macOS

# Download a file
aria2c https://example.com/file.tar.gz

# Download with 16 connections
aria2c -x 16 https://example.com/large-file.iso

# Download a torrent
aria2c file.torrent
```

## Introduction
aria2 is a lightweight, multi-protocol, multi-source download utility that operates from the command line. It supports HTTP/HTTPS, FTP, SFTP, BitTorrent, and Metalink, allowing you to download files from multiple sources simultaneously to maximize bandwidth usage.

## What aria2 Does
- Downloads files via HTTP/HTTPS, FTP, SFTP, BitTorrent, and Metalink protocols in a single binary
- Splits downloads into multiple segments and fetches them in parallel for faster transfer speeds
- Resumes interrupted downloads without re-downloading completed portions
- Provides a JSON-RPC and XML-RPC interface for remote control and integration with web UIs
- Supports downloading from multiple URIs for the same resource simultaneously

## Architecture Overview
aria2 is written in C++ for performance and low memory footprint. It uses an event-driven architecture with a single-threaded core and asynchronous I/O to manage thousands of concurrent connections efficiently. The download engine handles protocol negotiation, segment management, and disk I/O while exposing an RPC interface for external control.

## Self-Hosting & Configuration
- Runs as a daemon with `aria2c --enable-rpc --daemon` for persistent download management
- Configuration file at `~/.aria2/aria2.conf` stores default options like max connections and download directory
- Pair with web frontends like AriaNg or webui-aria2 for a graphical download manager experience
- Supports proxy configuration via `--all-proxy` or per-protocol proxy settings
- Session files allow saving and restoring download progress across restarts

## Key Features
- Extremely low memory usage (typically 4-9 MiB) compared to other download managers
- Protocol-agnostic segmented downloading accelerates transfers regardless of source type
- BitTorrent support includes DHT, PEX, encryption, magnet URIs, and selective file downloading
- Metalink support enables automatic mirror selection and integrity verification via checksums
- Built-in JSON-RPC/XML-RPC API makes it easy to build custom automation and UIs on top

## Comparison with Similar Tools
- **wget** — single-connection downloads without segmentation; aria2 adds parallel connections and multi-protocol support
- **curl** — focused on single transfers and scripting; aria2 handles queuing, segmentation, and BitTorrent natively
- **axel** — lightweight accelerator but lacks BitTorrent, Metalink, and RPC interface
- **transmission-cli** — BitTorrent only; aria2 handles HTTP/FTP downloads equally well

## FAQ
**Q: Can aria2 download from multiple mirrors simultaneously?**
A: Yes. Pass multiple URIs for the same file and aria2 fetches segments from each source in parallel, maximizing throughput.

**Q: How does aria2 compare in memory usage to graphical download managers?**
A: aria2 typically uses 4-9 MiB of RAM, far less than GUI-based tools like JDownloader or Free Download Manager.

**Q: Does aria2 support download speed limiting?**
A: Yes. Use `--max-download-limit` and `--max-upload-limit` to cap bandwidth per download or globally.

**Q: Can I use aria2 as a daemon with a web interface?**
A: Yes. Run aria2 with `--enable-rpc` and connect a frontend like AriaNg for browser-based download management.

## Sources
- https://github.com/aria2/aria2
- https://aria2.github.io/

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Source: https://tokrepo.com/en/workflows/asset-8ab069e2
Author: Script Depot