Alt Text

Provides a text alternative for an image in the HTML img tag, describing its content or function for accessibility and search engine context.

If you have ever stuffed 'keyword, keyword, keyword' into every image field expecting a ranking boost, you already know it does not work that way.

Key points

Describe what the image shows, not what you wish it would rank for.
Keep alt text under 125 characters; longer descriptions defeat screen readers.
Leave alt text blank only for decorative images that add no information to the page.
Use natural language — 'a red bicycle leaning against a brick wall' beats 'bicycle red brick wall'.
Add alt text to every informative image; missing alt text hurts accessibility and image seo.

One product image, two alt texts

An e-commerce site sells a blue wool coat. The developer writes 'blue coat wool men'. The accessibility specialist writes 'a long blue wool overcoat with toggle buttons, photographed on a model against a white background'. The developer's version passes basic search checks; the specialist's version tells a screen‑reader user what the coat actually looks like and passes the same SEO value. Google has not documented that one outranks the other, but only one serves a user who cannot see the photo.

Three things alt text is not

Not a ranking lever Google treats alt text as a weak relevance signal, not a guaranteed placement booster. A page with strong content can rank higher than one with perfect alt text but thin copy.
Not a caption A caption appears below the image and can repeat information. Alt text replaces the image when it fails to load; it should never say 'image of' because screen readers announce images already.
Not a keyword dump Stuffing the alt attribute with keywords confuses screen readers and may trigger spam filters. Write for a person who cannot see the image, then adjust the final words for the keyword if it fits naturally.

Four ways it goes wrong

Blank alt on key images Instructive images such as charts or product photos need description. Leave them empty only for purely decorative elements that add no meaning to the page.
Repeating nearby text If the page already describes 'a chart showing Q3 revenue growth of 12%', your alt text for that chart should not repeat the sentence verbatim — it should summarise what the visual shows.
Vague filler 'Photo', 'image', 'picture' — these help nobody. A screen‑reader user hears 'image, photo' and learns nothing about what the image contains.
Overly long descriptions Exceeding 125 characters forces screen readers to output a wall of text. Reserve depth for complex diagrams; otherwise, be concise.

What to check before saving

Image fails to load Disconnect your network, load the page, and read the alt text in the broken image area. If it reads like a sentence, you are done.
CMS settings Most platforms expose alt text in the media library or image block settings. Manually editing the HTML img tag works, but the CMS field is faster and less error‑prone.
Decorative image rule If the image exists only to separate sections or add colour, set the alt attribute to an empty string (alt="") so screen readers skip it entirely.

Common questions

What is alt text for images?

It is the text alternative inside the HTML img tag that describes an image for screen readers and appears when the image cannot load.

How to write alt text for images?

Describe the image's key content or function in plain English, keep it concise, and use natural language — not a list of keywords.

How to add alt text in WordPress?

Select the image in the block editor, open the settings panel, and type into the 'Alt Text' field. No HTML editing needed.

Sources

Google Search Central Official guidance on image indexing and alt text use.
WebAIM Accessibility-first guide with clear rules for each image type.
W3C WAI Authoritative tutorial on alternative text for web accessibility.
Ahrefs SEO-focused breakdown of alt text best practices and common mistakes.