aria2c Download Utility#
aria2c is a lightweight multi-protocol download utility. It supports HTTP(S), FTP, SFTP, BitTorrent, and Metalink, can open multiple connections per file, and resumes interrupted downloads.
Basic downloads#
# Download a file (HTTP, HTTPS, FTP, or magnet link)
aria2c https://example.com/file.iso
# Rename the output file
aria2c --out=ubuntu-24.04.iso https://releases.ubuntu.com/24.04/ubuntu-24.04-desktop-amd64.iso
# Resume an interrupted download
aria2c -c https://example.com/large-file.tar.gzParallel connections & speed#
# Open 8 connections to the same file (faster on slow servers)
aria2c --split=8 https://example.com/large.iso
# Set maximum download speed (bytes/sec; use K/M suffixes)
aria2c --max-download-limit=2M https://example.com/large.iso
# Download multiple files in parallel (not sequentially)
aria2c --force-sequential=false https://example.com/a.zip https://example.com/b.zipBatch downloads from a file#
# Download URLs listed one-per-line in a text file
aria2c --input-file=/path/to/urls.txt
# Download 1 at a time, resume partials, save to ~/Downloads
aria2c -j 1 -c -d ~/Downloads --input-file=/path/to/urls.txt
# Allow up to 4 parallel downloads from the list
aria2c --input-file=urls.txt --max-concurrent-downloads=4urls.txt format — each URI on its own line; options can follow the URI line:
https://example.com/file1.tar.gz
out=file1.tar.gz
https://example.com/file2.zip
https://mirror.example.com/file3.iso
dir=/tmp/isosBitTorrent & Metalink#
# Download via torrent file
aria2c https://example.com/ubuntu.torrent
# Download magnet link
aria2c "magnet:?xt=urn:btih:…"
# Download from torrent WITHOUT saving the .torrent file itself
aria2c --follow-torrent=mem "magnet:?xt=urn:btih:…"
# Seed ratio limit (stop seeding after uploading 2× what was downloaded)
aria2c --seed-ratio=2.0 ubuntu.torrentFTP / SFTP with authentication#
# FTP download with credentials
aria2c --ftp-user=myuser --ftp-passwd=mypassword ftp://ftp.example.com/pub/file.tar
# SFTP (requires private key or password)
aria2c --ftp-user=myuser sftp://server.example.com/home/myuser/data.tar.gzUseful flags reference#
| Flag | Default | Effect |
|---|---|---|
-c / --continue | false | Resume partially downloaded file |
-d DIR | . | Save directory |
-o NAME | from URL | Output filename |
-j N / --max-concurrent-downloads | 5 | Max parallel downloads |
-x N / --max-connection-per-server | 1 | Connections per server |
-s N / --split | 5 | Chunks per file |
--max-download-limit | 0 (unlimited) | Max speed (bytes/s) |
--max-upload-limit | 0 (unlimited) | Max seed speed |
-i FILE | — | URL list file |
--follow-torrent | true | mem = don’t save .torrent |
Checksum verification#
# Verify downloaded file against a known hash
aria2c --checksum=sha-256=<hash> https://example.com/file.iso