Alt text should convey what the image contributes to the page, not describe everything visible in it. The same photograph needs different alt text depending on why it is there. Decorative images should have an empty alt attribute rather than no attribute at all, and the most common failure is not bad description but a filename left where a description should be.
The question to ask
Not "what is in this picture". Rather: if this image did not load, what would the reader need to be told so they do not miss anything?
That reframe resolves most difficult cases, because it makes the answer depend on purpose rather than content.
A photograph of a technician beside a boiler illustrates several possibilities. On a page about your team, the useful information is who it is. On a page about boiler servicing, it is that the image shows the work being carried out. In a gallery of completed jobs, it is what was installed and where. Same photograph, three correct answers.
The categories
Decorative images
Background textures, dividers, images that repeat information already in adjacent text. These take an empty alt attribute, written as alt="", which tells assistive technology to skip them.
Omitting the attribute entirely is different and worse, since some screen readers then announce the filename instead, which is exactly the outcome the empty attribute prevents.
Informative images
Images carrying meaning the text does not. Describe the meaning concisely, not the composition. "Cracked cast iron drain pipe with root intrusion" rather than "a close-up photograph showing a pipe in a trench with soil around it".
Functional images
Images that act as links or buttons. Describe the destination or action rather than the graphic. A telephone icon linking to your number should read as something like "Call us", not "telephone icon".
This is the category most often got wrong, and it produces genuinely broken navigation for anyone using a screen reader.
Images of text
The alt text must contain the same words. Better still, avoid images of text entirely, since they are also unsearchable, unselectable, and blur when zoomed.
Complex images
Charts, diagrams, and maps generally cannot be served by a short attribute. Provide a brief alt describing what the image is, and put the substance in adjacent text or a caption where everyone can read it.
The common failures
- Filenames. Left by content systems that populate alt from the upload name. A screen reader announcing "IMG underscore 4471 dot jpeg" is the default state of a great many sites.
- "Image of" and "photo of". Redundant, since the technology already announces that it is an image.
- Keyword stuffing. Alt text written for search rather than for people. It reads as gibberish aloud, and search engines have long since discounted it.
- Repeating the caption. If text beside the image already says it, the image is decorative in that context.
- Excessive length. A paragraph of description is exhausting to listen to. Aim for a sentence.
- Empty when meaningful. The opposite failure, common where someone has been told decorative images take empty alt and applied it universally.
Does it help SEO?
Modestly and honestly: alt text helps search engines understand images, which matters for image search and contributes context. It is not a ranking lever, and writing it for machines produces text that fails the people it exists for.
Write it for a person who cannot see the image. The search benefit follows from accurate description anyway.
The test
Read your page aloud, skipping every image and reading its alt text in place.
If a sentence becomes nonsense, or a link becomes unidentifiable, or you find yourself saying "IMG underscore four four seven one", the alt text is not doing its job. This takes a few minutes per page and requires no tooling.
A useful related check: many browsers can disable images entirely. A page viewed that way shows exactly what a portion of your visitors experience, and it tends to be clarifying.
Frequently asked questions
What should alt text say?
What the image contributes to the page rather than everything visible in it. The useful question is what a reader would need to be told if the image failed to load so that they miss nothing, which makes the answer depend on the image's purpose in context.
Should decorative images have alt text?
They should have an empty alt attribute, written as alt equals two quotation marks, which instructs assistive technology to skip them. Omitting the attribute altogether is different and worse, since some screen readers then announce the filename instead.
How should I write alt text for an image that is a link?
Describe the destination or action rather than the graphic. A telephone icon linking to your number should read as Call us rather than telephone icon, since the reader needs to know where the link goes, not what the picture depicts.
How long should alt text be?
Roughly a sentence for most images. Longer descriptions are tiring to listen to, and where an image genuinely requires extensive explanation, such as a chart or diagram, the substance belongs in adjacent text or a caption where everyone can read it.
Does alt text help with SEO?
Modestly. It helps search engines understand images and contributes context, particularly for image search, but it is not a ranking lever. Writing it for machines produces text that fails the people it exists for, while accurate description delivers any search benefit anyway.
How can I check my alt text is working?
Read the page aloud, skipping each image and reading its alt text in its place. If a sentence becomes nonsense, a link becomes unidentifiable, or you find yourself reading out a filename, the alt text is not doing its job.
West Coast Media Solutions Inc. builds websites for businesses across Canada. Platform policies change and enforcement varies; where legal actions are described they are identified by jurisdiction, since much of the published material on these topics is American and does not apply directly in Canada. This is general information rather than legal advice.
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