Why Every Image on Your Site Needs Alt Text
Alt text is the written description attached to an image. It is read aloud by screen readers, shown in place of the picture when it fails to load, and used by search engines to understand what an image contains. The Alt Text Auditor checks a block of HTML and tells you which images are missing it.
Three jobs at once
Accessibility first. Someone using a screen reader hears the alt text where you see the picture. No alt text means either silence or, worse, the file name read out character by character - "D S C underscore zero four nine two dot jpeg". If the image carried information, that information is simply gone for that reader.
Resilience second. Images fail. A slow connection, a broken path, a blocked host. The alt text is what appears in the gap, and a page with good alt text still makes sense when none of the pictures load.
Search last, and it really is last. Google reads alt text to understand an image, which matters for image search and gives a little context to the page. It is a genuine benefit and it is not the reason to do it.
How to write it
Describe what the image shows, in a sentence, as if to someone who cannot see it. "A red cafe awning over a pavement table" tells someone something. "Image" tells them nothing. "Cafe awning photo picture outdoor seating restaurant table chairs" tells them nothing either and looks like keyword stuffing, which it is.
Three habits to drop. Do not start with "image of" or "photo of" - the screen reader already says it is an image, so you are making the user hear it twice. Do not repeat the caption, since the reader hears both. And do not stuff keywords; write the sentence you would say out loud.
Length: a short sentence is usually right. If the image genuinely needs a paragraph - a chart, a diagram, a data table as a picture - put that explanation in the page text where everyone can read it, and keep the alt text brief.
The images that should have empty alt text
This is the part most people get wrong. A purely decorative image - a divider, a background flourish, an icon beside a label that already says the same word - should have an alt attribute that is deliberately empty. That tells a screen reader to skip it. Leaving the attribute off entirely is different: the reader then falls back to announcing the file name.
So every image needs an alt attribute. Not every image needs words in it.
Common questions
What about an image that is a link?
Describe where the link goes, not what the picture looks like. The alt text is the link text for anyone who cannot see the image.
Does alt text help my rankings?
A little, and mostly in image search. Write it for the reader and the search benefit follows.
How do I find images missing alt text?
Paste your page HTML into the auditor and it flags every image tag that has no alt attribute or an empty one you did not intend.
Should alt text end with a full stop?
It helps. Screen readers pause at punctuation, so a sentence reads as a sentence.
Want to know which of your images are missing it?