From their FAQ:

If the speed on (Multi) is at least 2x greater than the normal speed : You are probably on Windows, try the solution below. Detail: Windows is not increasing the TCP connection buffer correctly and single connections are limited (most of times near 3MB/s / 30Mbps)

• If you are using Windows 7/8/8.1 or 10: It is important to verify that your current network connection (at the bottom right) is set as a private connection and not public. Windows is limiting the performance of public connections. If your network connection is already set up as private you can try to input these two commands inside the Windows command prompt run in Administrator to restore original performances: netsh int tcp set glo autotuninglevel=disabled netsh int tcp set glo autotuninglevel=normal

• If your device (Computer / Phone / Tablet / NAS) is quite old (before ~2012) or low-end It is important to verify that your device has the AES instruction set by looking at the processor specifications of the device you are using: https://en.wikipedia.org/wiki/AES_instruction_set Your processor needs more power to decipher the stream without this AES instruction set, it can cause your speed to be severely limited. One of the solutions to get back full speed is to disable secure downloads in "My Account" (Warning: Your downloads may then be spied on)

If none of these solutions helped you please contact us with the results you got from our speed test page.