Me and other developers at our company are struggling with "title" and "alt" attributes. In the past, we added "title"-Tags to all links for SEO purposes (although some of them were annoing talking about usability) and "alt"-Tags on every image on the site, because HTML4 spec said so.
- Are "title" and "alt"-Tags still required?
- If they're not required, do they still have effects on SEO?
Check the HTML specification to see what is/isn’t required:
aelement: The (global)titleattribute is not required.imgelement: Thealtattribute is required in most cases (exceptions).
(Questions about the SEO effect are off-topic on Stack Overflow. They can be asked on Webmasters SE.)
alt attribute on img is always required except when it can't be provided (e.g. when users are allowed to upload images and you can't ask them to upload an alt text...)'; why alt is required, why is good to be provided and when you can leave empty string as value examples here
title attribute on link element is not required; check out link attributes
Yes In this version it is necessary too because of HTML5 Validation and Search Engine Optimization.
来源：https://stackoverflow.com/questions/21206735/alt-attribute-on-images-and-title-attribute-on-links-required-in-html5