The following modules and themes have been removed from Drupal 8 core.
|Module or theme||Use instead|
|Blog module||Use content types, fields, and the Views module (now in core) to build a blog. The legacy Blog module is also now available as a contributed project.|
|Dashboard module||The Dashboard module is now available as a contributed project.|
|Design test module|
|Garland theme||The Garland theme is now available as a contributed project.|
|Number module||See Move email and number field types to \Drupal\Core\Field, remove modules.|
|List module||See List module merged with Options module.|
|OpenID module||The OpenID module is now available as a contributed project.|
|Overlay module||The new Drupal 8 toolbar now includes a contextually aware "back to site" button that serves the same use-case as overlay by allowing site users to return from the admin context to the page that they were on.|
|PHP filter module||See PHP Filter module removed from Drupal core for more information.|
|Poll module||The Poll module is now available as a contributed project. There are also other contributed modules that provide polling functionality.|
|Profile module||Attach fields to users or use the contrib Profile 2 module.|
|Trigger module||The Rules contributed module provides similar functionality. The legacy Trigger module is also now available as a contributed project.|
Also support for user signatures moved to contrib module https://www.drupal.org/project/signature
See also Modules (or Drupal 7 module-equivalent features) added to core in Drupal 8 for the modules added to Drupal 8 core.