Alt text, short for alternative text, is a written description of an image that screen readers speak aloud for visually impaired users and search engines read to understand what the picture shows. It lives in the HTML alt attribute of the image tag, and it appears on the page whenever the image itself fails to load. Writing it well takes seconds per image, and it is one of the most skipped jobs in on-page SEO.
The short version
- Alt text describes an image for screen readers and search engines.
- Keep it specific and under 125 characters.
- Decorative images get an empty alt attribute, not a description.
- Never start with "image of", and never stuff keywords into it.
- 2.2B people live with a vision impairment
- 22% of Google searches are image searches
- 125 characters is the practical ceiling
- 55% of site images ship with no alt text
Why alt text matters
Alt text does three jobs at once. It makes your content usable for people who browse with screen readers, which is also what ADA and WCAG accessibility standards require and what accessibility lawsuits test for. It gives Google Images the words it needs to rank your pictures, which is real traffic on visual queries. And it keeps the page readable when an image breaks or a connection is slow, because the description renders where the picture should have been.
The syntax is a single attribute:
<img src="dog-frisbee.jpg" alt="Golden retriever jumping to catch a red frisbee in a park">How to write alt text that works
- Describe what the image actually shows. "Dog" is vague. "Golden retriever puppy sleeping on a blue couch" tells the truth in detail.
- Keep it under 125 characters. Screen readers may truncate past that, and longer usually means padding.
- Include a keyword only when it fits. If the picture genuinely shows your target topic, name it. Never force one into an unrelated photo.
- Skip "image of" and "photo of". Screen readers already announce that it is an image.
- Match the context. The same photo can need different alt text on a product page than in a tutorial, because its job on the page changed.
- Give charts their conclusion. For a graph, state the takeaway ("organic traffic up 150% over 12 months"), not every data point.
- Do not repeat the caption. If a visible caption exists, the alt text should add information, not duplicate it.
Good and bad alt text on the same image
- Good. alt="Nike Air Zoom Pegasus 40 men's running shoes in black and white". Brand, model, product type, and color. Useful to a shopper who cannot see the photo.
- Bad. alt="shoes". True but useless. It could describe half the store.
- Bad. alt="IMG_4532.jpg". A file name describes nothing. This is what auto-inserted alt text often looks like.
- Bad. alt="nike shoes buy now best running shoes cheap". Keyword stuffing reads as spam to Google and as gibberish to a screen reader user.
- Good. alt="" on a decorative divider line. The empty attribute tells screen readers to pass over an image that carries no information.
One special case worth knowing. When an image is a link, like a logo that points to your homepage, the alt text should describe the destination ("Egochi homepage"), because for a screen reader user it is the link text.
Where to add alt text on your platform
In hand-written HTML, alt is just an attribute on the img tag. WordPress exposes an "Alternative text" field in the media library and in the image block sidebar. Shopify has an alt field on every product image, and Wix and Squarespace both surface it in image settings. The work is rarely technical. It is editorial, which is why it gets skipped.
To find the gaps, crawl your site with a tool like Screaming Frog and filter images by missing alt text, or run any page through the WAVE accessibility checker. On most sites we audit, more than half the images come back empty.
Where alt text fits in the bigger picture
Alt text is one piece of image SEO, next to descriptive file names, compression, and modern formats, and the whole family rolls up into on-page SEO. If your pages lean on original photography, diagrams, or product shots, the combination of honest alt text and fast-loading files is traffic other sites are leaving on the table.
Questions people ask about alt text
What is alt text used for?
Two things. For accessibility, it gives screen reader users a description of what an image shows. For SEO, it tells search engines what the image is, since crawlers cannot see pictures. It also displays in place of the image when a file fails to load.
How long should alt text be?
Aim for 125 characters or less. Screen readers may cut off longer descriptions, and anything past that length usually means you are describing more than the image actually shows. Be specific, then stop.
Does alt text help SEO?
Yes. Alt text is one of the main signals Google Images uses to rank pictures, and image searches make up roughly a fifth of all Google searches. It also adds context that supports the rankings of the page the image sits on.
Should every image have alt text?
Every image that carries information should. Purely decorative images, like divider graphics and background flourishes, should ship with an empty alt attribute (alt="") so screen readers skip them instead of announcing noise.
What is the difference between alt text and a caption?
A caption is visible to everyone on the page. Alt text is read by screen readers and search engines, and only appears visually if the image fails to load. When an image has a caption, the alt text should add to it, not repeat it word for word.
