Images are part of your content. You can use the images for two main reason:
- To add important information (to explain something more vividly and to visualize what you have put in text).
- To decorate your article (to make it more eye-catching and easier to remember).
Alt text implementation depends on the purpose of using the image:
Alt Text for Accessibility and Usability:
- Include descriptive alternative text for content-sensitive/meaningful images (i.e. those that add important information to the text): alt text is what people who turned off displaying images will see and blind people will hear in place of the image.
- If an image was used for purely decorative purposes, assign an alt text to null value (alt=””) so that the image could be completely ignored by screen readers.
Alt Text for SEO:
- Add keyword-optimized alt text:
- To enhance the page keyword prominence;
- So that people referred by image search results were tempted to visit the page (If you were searching for link building, for example, which image would be more interesting for you: a graph detailing the link building process or a chain symbolizing the process which is how posts on link building are decorated?).
- Skip the alt text at all (in this cases I usually use title instead). You will need to use empty alt text (alt=””) though for validation purposes though.