Every image on your page has a hidden description attached to it — or at least, it should have. That description is called alt text, short for “alternative text”. Sighted visitors never see it. But two very important audiences rely on it completely: screen readers, which read it aloud for visually impaired visitors, and Google, which uses it to understand what the image shows.
Alt text is a small job that feels invisible when done right and embarrassing when skipped. The good news: writing good alt text takes about ten seconds per image once you know the formula.
What alt text actually does
Alt text has two jobs, and they matter equally:
- Accessibility. When a screen reader reaches an image, it reads the alt text aloud. Without it, the listener hears the image filename instead — something useless like “IMG_4821.jpg” — or nothing at all.
- SEO. Google cannot see your images. Alt text is one of the main signals it uses to understand and index them, and a key factor in whether they show up in Google Image Search.
Good alt text is a rare case where doing the right thing for people and doing the right thing for search engines are exactly the same action: a clear, honest description of the image.
The 3-part formula
Most good alt text follows the same shape:
- What it is — the main subject, in plain words. “Golden retriever puppy”, not just “dog”.
- What it is doing, or the key detail — “sleeping on a blue blanket”, “typing on a laptop”.
- Context, only if it matters — where it is, or what it is for. “In a bright modern office”.
Keep it short: roughly 8–15 words is usually enough. A screen reader reads every word aloud, so a long paragraph slows down every listener who reaches the image. Say what is in the image, then stop.
Before and after: 5 rewrites
- Filename → description
- Before: IMG_4821.jpg
- After: “Golden retriever puppy sleeping on a blue blanket”
- Why it works: a screen reader can finally say something useful, and Google finally knows what the image is.
- One vague word → specific
- Before: “team photo”
- After: “Four colleagues smiling in a bright modern office”
- Why it works: the listener can picture the image; “team photo” could be anything.
- “Picture of” filler → straight to the point
- Before: “Picture of a chocolate cake”
- After: “Chocolate layer cake with berries on a white plate”
- Why it works: screen readers already announce that it is an image, so “picture of” wastes words.
- Keyword-stuffed → natural
- Before: “best cheap running shoes buy running shoes online running shoe sale”
- After: “Red running shoes on a white background”
- Why it works: the keyword appears once, naturally — stuffed alt text is a known spam pattern that search engines discount.
- What you wish it showed → what it actually shows
- Before: “The joy of remote work”
- After: “Woman typing on a laptop at a cafe table”
- Why it works: alt text describes the image, not the feeling you want it to convey.
When to leave alt text empty
Not every image needs a description. An image used purely for decoration — a background texture, a divider line, a stock photo that adds no information — should have an empty alt attribute (alt=””). That tells screen readers to skip it silently instead of wasting the listener’s time announcing something irrelevant.
The quick test: if the image adds meaningful information, describe it. If removing it would change nothing, leave the alt text empty.
5 mistakes to avoid
- Leaving it blank. A blank alt attribute means screen readers read the filename out loud — usually the worst possible description.
- Writing “image of” or “picture of”. Screen readers already say “image” before reading your text. Start with the subject.
- Keyword stuffing. Repeating a keyword five times in alt text is a spam pattern, and a broken experience for real screen-reader users.
- Using the same alt text on every image. Each image needs its own description. Identical alt text across a page is a sign it was copied, not written.
- Describing the wrong thing. Alt text should say what is actually in the image — not the caption, the surrounding paragraph, or what you hope the reader feels.
Checklist before you publish
- 8–15 words, specific and literal
- Main subject named clearly, in plain words
- Keyword included only if it naturally describes the image
- Unique to this image — not copied from another
- Decorative images use empty alt text (alt=””)
- Read it aloud — if it sounds like a real description, it is
Try it on your own images
Pick one image on your site and write its alt text using the 3-part formula above: subject, key detail, context if it matters. Or get a head start with the free Image Alt Text Generator — describe the image in a few words, choose the image type, and it gives you four natural options to pick from.