Should image alt text have punctuation?
By using proper punctuation such as commas or period characters, this helps screen readers describe the image in more of a “human” sounding approach. Commas will add a short break in between announcing content. Placing a period character at the end of a sentence will cause the screen reader to, “take a breath.”
What are the requirements for alt text?
As a rule of thumb: avoid writing text alternatives longer than 100 characters. Having long alt text will result in a poor user experience for those using screen readers. If the image requires a lengthier description, it is better to describe the image in the content and provide a shorter alt text.
How should alt text be written?
The alt text shouldn't be longer than a sentence or two—most of the time a few thoughtfully selected words will do. Consider what is important about an image. For example, important context might be the setting, the emotions on people's faces, the colors, or the relative sizes.