Key Takeaways
- Good alt text answers one question: "What would I tell a friend about this image?"
- Lead with the subject, then the distinguishing detail (color, variant, angle).
- Use
alt=""for decorative images — don't describe them. - Keep it to one sentence; skip the filename and "image of".
- Self-review with the checklist at the end.
In This Article
The 4-Question Decision Flow
Before writing a word, answer these in order. They decide whether you write alt text at all, and what it should say.
- Does the image convey information? If no (divider, spacer, background), use
alt=""and stop. - What is the single most important thing it shows? Name that subject first.
- What detail would a friend point out? Color, variant, angle, emotion, text-in-image.
- Is the same info already in the text next to it? If yes, keep alt short or empty to avoid repetition.
The One-Sentence Formula
For informative images, write one sentence:
[Subject] + [distinguishing detail] — e.g. "Navy wool blazer with gold buttons, front view"
That's it. No "image of", no file name, no marketing claims the picture can't prove. For product images specifically, our ecommerce alt text guide adds the variant/angle habit that scales to catalogs.
Before / After Examples
| Weak | Good |
|---|---|
| "image1.png" | "Woman in navy wool blazer, gold buttons, smiling" |
| "product image" | "Beige organic cotton tote bag with long handles" |
| "buy cheap t-shirt online best price" | "Heather grey cotton crew-neck t-shirt, front view" |
| "logo" | "Scan Alt" (or alt="" if the name appears in adjacent text) |
For 40+ more examples across product images, logos, charts, and decorative images, see our alt text examples guide.
Common Mistakes
- Starting with "image of" — screen readers already announce "image", so it's redundant.
- Pasting the file name — "DSC_4821.jpg" helps no one.
- Keyword stuffing — reads as spam; see alt text vs title text for why the title attribute is not the place for this either.
- Describing decorative images — use
alt=""instead. - Writing a paragraph — one sentence; long alt gets truncated by some readers.
Self-Review Checklist
Before you publish, confirm:
- Decorative images use
alt="". - Informative images have a real alt attribute (no blanks).
- Alt leads with the subject, then the key detail.
- No file names, no "image of", no stuffing.
- Length is one sentence (under ~125 characters).
- Alt conveys the same info as the image.
Run the same six checks across a whole page with our free alt text checker — it flags missing, empty, vague, and overlong alt automatically.
Check your alt text in one scan.
Paste any URL and get missing, empty, vague, and overlong alt flagged — free, no signup.
Free Alt Text ScanFAQ
What is the best format for alt text?
A single concise sentence that names the subject and the distinguishing detail a sighted user would notice: product, color, variant, angle. Lead with what matters. Avoid the file name, avoid 'image of', and avoid stuffing keywords.
Should alt text include keywords for SEO?
Only if the keyword fits naturally as a description. Alt text is primarily an accessibility feature; Google reads it as an image-understanding signal. Writing 'blue cotton t-shirt' already contains the useful keyword without forcing it. Stuffing reads as spam to both screen readers and search engines.
How do I write alt text for a decorative image?
Use empty alt (alt="") so screen readers skip it. Decorative dividers, background art, and pure spacing icons carry no information, so a description only adds noise. Reserve real alt text for images that convey meaning.
Conclusion
Good alt text is not a writing talent — it is a habit. Decide first (decorative or informative), then write one sentence that names the subject and the detail a friend would point at. Skip the filename, skip "image of", skip the stuffing. Use the six-point checklist, and let a scanner catch what you miss at scale. Done consistently, it covers accessibility and search in the same pass.
Sources & References
- W3C. (2023). "WCAG 2.1 — Success Criterion 1.1.1 Non-text Content." w3.org/TR/WCAG21
- WebAIM. "Alternative Text." webaim.org/techniques/alttext
- Google Search Central. (2024). "Google Image SEO Best Practices." developers.google.com/search