Where can I download previous versions of Craft? Auto-updating is great and all, but sometimes you need to roll-back to a previous version or build of Craft for whatever reason.  Where can you download these?
In Craft 2:

You can download previous versions of Craft from https://download.craftcms.com.

Previous versions and builds of Craft are available with the following URL format in both zip and tar.gz versions:

http://download.craftcms.com/craft/{version}/{version}.{build}/Craft-{version}.{build}.zip (or .tar.gz)


For example, if you wanted Craft 2.1 build 2557 in tar.gz format, it would be 

http://download.craftcms.com/craft/2.1/2.1.2557/Craft-2.1.2557.tar.gz


Note that downloading Craft releases directly still binds you to Craft’s license agreement, and keep in mind that Craft does not support rolling back to previous versions automatically.

If you’ve already updated your site past a certain release and want to go back to it, you’ll need to find and restore a database backup that was created with the version you’re going back to.

In Craft 3:

You can download previous Craft 3 versions in several ways:


From pre-built packages in this format:


http://download.craftcms.com/craft/{majorVersion}/Craft-{majorVersion}.{minorVersion}.zip (or .tar.gz)

For example:

http://download.craftcms.com/craft/3.0/Craft-3.0.26.1.zip (or .tar.gz)



Directly from the Craft Github repo release page
Since Craft 3 is Composer based, you can modify your composer.json's craftcms/cms line to install the previous version you're looking for.