DownThemAll! is a popular download manager for Firefox Web browser supporting multi-part downloading with ability to pause and restart downloads without losing data. A common problem encountered while using DownThemAll! is the dreaded “no free space” error. Before initiating a download, DownThemAll! makes sure you have enough disk space.

Let’s say you want to download a 500Mb file to C:\downloads\, DownThemAll! will make sure you have 500Mb of available space in the destination directory. In addition to that, DownThemAll also needs disk space in the temporary directory where it hold all downloaded fragmets of the file. Once all the fragmets are downloaded, they are re-combined into the final file. The temporary directory also needs 500Mb of free space, so that DownThemAll! can pre-allocate enough space (to make sure that some other application does not use it all up while the download is running). The temporary directory can be specified by opening DownThemAll! download manager, clicking on “Preferences” -> “Advanced” tab -> Temporary files.

DownTheAll! Preferences window

When you run into the “no free space” error, you need to check a few things:

1. Make sure the primary download directory (C:\downloads\, in our example) has the required free space.
2. Make sure that the temporary directory used by DownThemAll! has enough free space.
3. Make sure that both the download and the temporary directories have read/write permissions for your user account.
4. Make sure that the your system disk is not running very low on free space.

When using DownThemAll! to download very large files, you may notice a short (or not so short, depending on the file size) delay when the download starts. Temporarily, Firefox may become unresponsive. This is caused by DownThemAll! attempting to pre-allocate disk space to hold your large download. This problem can be eliminated by specifying the temporary directory outside of the system disk, such as an external disk, some other hard drive, or a high-speed network share.

Because DownThemAll! splits a large download into multiple streams (a feature you can control via the Preferences menu), multiple streams of data are being written to your hard drive simultaneously. This can slow down your computer when the download is in progress. If you have a fast network connection and running multiple donloads at the same time, this performance degradation may be significant. It is, therefore, a good idea to specify both the download destination and the temporary folder outside the primary system disk. This way your downloads will run faster, you system will be more responsive, and there is no danger of crashing your system by using up all available disk space.