Creating high quality and original images (as explained in tip #4 of this article) is important. But many people forget to add alt text to their images.
Alt text, or alternative text, is used to display text that describes an image to “alternative” sources.
Primarily, its goal is to make images more accessible to the blind who use screen readers, to make the web much more accessible per W3C accessibility guidelines.
It lets you specify an image description that is fed through an audio-based prompter, which tells people with low or no vision what is currently on the page.
The secondary goal for alt text is to describe the image for people who have decided, for whatever reason, to turn off images in their web browser application.
As a rule, alternative text should include targeted keyword optimization in a context that describes what the image is about. If no alternative text exists for the image, it will be displayed as an empty image.
Google uses alternative text as a focus when they are trying to understand what the image is about. This is why adding alt text is important if you want your images themselves to rank in Google.
This is less critical if you are using original but fairly generic images. But suppose you create an illustration of a concept in your newsletter or even a more complex graphic like an infographic.
For example, if I include a custom graphic showing writer earnings on a specific blogging platform (as I did in the article (Medium vs. Quora), adding alt text helps make that image, and in turn the article, more accessible to readers.