Alternative text (also called alt text) is crucial for accessibility. It explains the purpose of visual content for people who use screen readers (software that converts text to audio) and other users who can’t perceive visual content.
Alt text is also important for search engine optimization (SEO). Search engines need accurate alt text in order to index and rank images — and to rank the websites that contain those images.
As we’ve discussed in other articles, the best practices of SEO overlap with the best practices of accessibility. Alt text is an excellent example: By improving the way that you write alt text, you can improve your search presence while providing your users with a better experience.
Below, we’ll explain a basic process for collecting, evaluating, and fixing your website’s alt text.
1. Collect alt text for every image on your website
The goal is to have a spreadsheet that contains the URLs of each image for each web page, along with their alt text.
If your website is relatively small, you can collect alt text manually through your website’s content management system (CMS). Of course, if you’ve got thousands of images, this isn’t a practical option.
At scale, the quickest way to collect alt text is to use an SEO crawler like Screaming Frog, Moz, or SEMrush (here, we’ll note that the Bureau of Internet Accessibility does not endorse specific SEO tools).
Screaming Frog is especially useful for content audits. The free version has a crawl limit of 500 web pages; here’s a guide from Screaming Frog that explains how to find image alt text and attributes with their crawler.
Related: Perform a Page Title Audit to Improve Mobile & Website Accessibility
2. Add alt text where necessary — but remember, some images don’t need alt text
Once you’ve got a list of images and their attributes, you’ll probably notice that some images don’t have alternative text. If the images are meant to convey information, prompt a user interaction, or perform another important function, you’ll need to add alt text.
However, images do not need alt text if they are:
- Purely decorative, with no important information for users.
- Already described on the page in text.
- Background images that are not the primary contact.
In these cases, images still need a null alt attribute, which tells screen readers and other assistive technologies that the image can be safely ignored. Here’s an example of a null image alt attribute:
<img src="/decorativeimage.gif" alt="">
For more guidance, read: How Do I Know If an Image Needs Alt Text?
3. Look for common alt tag mistakes
The next step is to review your existing alt text. Ideally, each description will describe its image concisely and accurately — but practically, you’ll probably find opportunities for improvement.
Some tips to keep in mind:
- If alt text begins with “image of" or “picture of,” revise it. Screen readers will identify the image for the user — alt text that reads “image of a red apple" is redundant. “Red apple" is better alt text.
- Avoid long, drawn-out descriptions. The text should quickly describe the image using common terminology.
- Double-check your spelling and punctuation. Screen readers are powerful tools, but they’re not perfect — they can’t always pronounce misspelled words.
- If images contain text, that text should be part of the alt text.
- Never use “company logo" as the alt text for your company’s logo. Use your company’s name instead — this is one of the most common image alt tag mistakes, so avoid it.
To thoroughly update your alt text, you’ll need to view the images within context. That means opening up each webpage and ensuring that the text describes the purpose of the image.
For more guidance, read: What is the Best Way to Write Alternative Text?
4. Have a plan for regular alt text audits
Once you’ve rewritten your alt text, you’re in the clear — for the time being. If you rebrand your company or redesign your website, you’ll need to audit your content again.
And if you’re not the only person who updates your website, you’ll need to make sure that every content creator understands the importance of alt text and how to write accurate descriptions.
The good news: When you’ve got a process in place, writing alt text becomes easier — and your users will certainly appreciate your hard work.
To find and fix other common accessibility issues (and improve your SEO in the process), download The Definitive Website Accessibility Checklist, an in-depth checklist with tips for ensuring digital compliance.
