Alt text, or alternative text, is a brief description of an image or other visual content that’s read aloud by screen readers to help people with visual or cognitive disabilities understand the content. Alt text is an essential part of making digital content accessible.
The aim of Alt text is to make sure that anyone using alt text through assistive technologies can get the same information from the description of an image as someone who relies on the visuals.
According to the Royal National Institute of Blind People (RNIB), two million people in the UK live with significant sight loss, and many of these will use assistive technologies that rely on alt text.
So that’s the what and why, but what about the how?
There are no set rules for writing alt text. That said, adding ‘bad’ alt text is better than adding none at all. But why write bad alt text when you can write good alt text?
Hayley Kellard owner of online business Dotty About Braille (and long-time Twitter friend) which sells braille cards says “I’m not an accessibility expert, I’m just a small business owner who happens to be visually impaired and have visually impaired family members so I understand how important alt text is.”
“Firstly, I would always recommend not making any assumptions about what blind or visually impaired people might need or not need, and just try to offer them the same online experience as anyone else via alt text.”
“The main point of alt text is simply to get across the main point of the image. But at the same time, particularly when it’s a product for sale, you need to provide enough to make a purchase decision. No alt text. No sale.”
“Also, it’s really important to not start your alt text description with “this is an image of” or “this is a photo”, it’s not necessary as the screen reader will tell the user it’s an image.”
Some more tips from me
- Try to keep the alt text short and very clear. Yes, concise simple writing can be tricky, but the more you practice the better you will get.
- Don’t include every detail in a busy image. Give an overview and focus on the main theme/image.
- Don’t stuff with keywords.
- End with a full stop. The screen reader needs this to denote the end of the alt text description.
- Context is important. An image could have widely different alt texts when used in different scenarios.
- Remember as well that alt text will be displayed if an image fails to load. This is a good sense check as to whether what you have written makes sense in the context.
- Alt text is also read by search engines so is good for SEO – see link below for more on this.
This is a non-exhaustive short intro to the what, why and how of alt text. Now you have no excuses not to use alt text (note very much to self here too).
Useful resources
Lengthier blog from Hayley Kellard on alt text
Google image SEO best practice