Trying to update to 1.6.10 package fails

Often I get the message that I can update the board package. When I try that, I get the error that the file cannot be downloaded. The URL that is used is

However does work but the IDE doesn’t use that URL, it uses the other one.

In the IDE under File->Preferences->Additional Board Manager URLs you can either use the standard URL:

or the test URL:

The standard URL contains the official releases (currently on v1.6.9) and the test URL will also include unofficial releases which may be subject to further changes. Currently, there is a v1.6.10 test version.

Unless you need to use some feature that has not made the latest official release, I would recommend sticking with the standard URL. Because the test releases are subject to change, this can confuse the board manager and how it caches the files. If you see a CRC mismatch error, this can usually be fixed by clearing the board manager cache directory.

On a PC this directory is located in: