How to Limit Download Speed in aria2 Session?

This article provides a quick, actionable guide on how to restrict the maximum download speed for a specific aria2 session. Whether you are running the utility via the command line or managing it through a configuration file, you will learn the exact flags and parameters needed to cap bandwidth usage temporarily or permanently. By managing these limits, you can prevent aria2 from consuming your entire network bandwidth, ensuring other applications remain responsive.

Setting the Limit via Command Line

The quickest way to set a maximum download speed for a specific aria2 session is by passing the --max-download-limit flag directly when starting the command in your terminal. This limit will only apply to that specific instance and will expire as soon as the session closes.

You can specify the speed using standard size suffixes:

Here is the standard command structure:

aria2c --max-download-limit=500K "YOUR_DOWNLOAD_URL"

In this example, the download speed for the session is strictly capped at 500 KB/s. If you want to allocate a larger pipe, such as 2 megabytes per second, you would format it like this:

aria2c --max-download-limit=2M "YOUR_DOWNLOAD_URL"

Setting the Limit via Configuration File

If you prefer not to type the flag every time but still want a specific session—like a daemon session—to respect a bandwidth cap, you can define this rule within your aria2 configuration file (typically named aria2.conf).

Add the following line to your configuration file:

max-download-limit=1M

When you want to run a session using these specific configuration rules, point aria2 to that file using the --conf-path flag:

aria2c --conf-path=/path/to/your/aria2.conf "YOUR_DOWNLOAD_URL"

Changing Limits Dynamically During a Session

If you have an active aria2 session running as a background daemon with the Remote Procedure Call (RPC) feature enabled, you do not need to restart the session to change the speed limit. You can alter the maximum download speed on the fly using the aria2.changeGlobalOption method via an RPC client or a simple curl command.

Here is an example of a JSON-RPC request sent via curl to dynamically change the session limit to 300 KB/s:

curl http://localhost:6800/jsonrpc -d '{"jsonrpc":"2.0","id":"qwer","method":"aria2.changeGlobalOption","params":[{"max-download-limit":"300K"}]}'

By utilizing these three methods—command-line flags, configuration files, or RPC inputs—you gain total control over how much bandwidth any given aria2 session is allowed to use.