You may be familiar with the alternative text (alt) attribute that appears in <img> tags. The purpose of alt attributes is to provide a description of the contents of an image file. This description will appear when a user cannot see the image in their browser, when the image is searched on search engines, and in screen readers. But it is very easy to forget to include this text in your images and that is bad news for accessibility and SEO.
 
In Drupal 8, alt attributes are now set to required by default on images. The same goes for such elements like user images and image fields. Such a task in Drupal 7 would have required you to download modules or modify the code yourself.
 
This is a big win for accessibility, as the alt attribute is often overlooked on websites, but is essential to many disabled users. And really the only downside is that users have to spend a bit of extra time writing out alt text for those images.

Alt text is really the low hanging fruit of accessibility. So often it is ignored by web developers and content editors when creating a site. Having the defaults for alt text enabled by default just makes it easier for content editors to produce better sites. This default also makes Drupal 8 conform closer to Authoring Tool Accessibility Guidelines (ATAG) 2.0.

See more about this series on Drupal 8.