Title Tooltip

The "title" attribute is NOT an accessible "tooltip".

HTML title attributes are often perceived as an accessibility bonus, but the opposite is true. Content being put in the title attribute is being hidden from many of your users (see below). If information is being hidden from your users, and you are okay with that, then the information is probably not necessary in the first place.

HTML 5.1 includes general advice on use of the title attribute:

Relying on the title attribute is currently discouraged as many user agents do not expose the attribute in an accessible manner as required by this specification (e.g. requiring a pointing device such as a mouse to cause a tooltip to apear, which excludes keyboard-only users and touch-only users, such as anyone with a modern phone or tablet).

The W3C states that:

Implementing this technique (supplementing link text) with the title attribute is only sufficient if the title attribute is accessibility supported (it is not, as stated above). If the value of the title is essential to understanding the purpose of the link for all users, then the content of this attribute needs to be available to all keyboard users (not only those with text-to-speech software) for this technique to be accessibility supported.