Speed and bottlenecks

Rapidly does not promise a speed. It measures what your connection and the server allow, and uses that. This page explains how, and how to read what it tells you.

How connections are chosen

Rapidly starts with a few connections and watches the total speed over short windows. If another connection raises the total by a meaningful amount, it adds more. If more connections stop helping, or make the download slower, it takes some away. For one site it never opens more than 32 connections by default.

When a connection finishes its part, it takes over half of the biggest part still left on another connection ("work stealing"), so the last piece does not wait for one slow connection.

A connection that stays below 35 percent of the speed of the others for 10 seconds is replaced by a new one.

What each bottleneck message means

Open a download's Details to see what limits it right now.

• Single connection cap: the server limits each connection, and adding connections is still helping. Let it run.
• Server total cap: the server limits the total speed it gives you. More connections will not help. Try another time, or add a mirror.
• Your link is full: your own internet connection is already used up. Pause other downloads or streaming, or set a limit so other things keep working.
• Disk bound: your disk cannot save data as fast as it arrives, so Rapidly slows the download on purpose. When 256 MB of data is waiting to be written, it pauses reading from the network until the disk catches up. Choose a faster drive for the download folder.
• Processor bound: the computer's processor is the limit. Close heavy programs, or lower the connections in Settings.
• Unknown: Rapidly is still measuring, or no single cause stands out yet.

Polite mode

Polite mode uses at most 4 connections per download. Use it for servers that complain about many connections, or when you want other people on the same network to keep working smoothly.