♿ Accessibility · SEO · AI Productivity
AI Tool to Write Alt Text for Images in Bulk
(Method + Prompts)
You have 80 product photos, or 40 old blog images, and none has alt text. Writing each one by hand takes a long time. An AI chatbot can write the first draft for you. But a person must check every line. This guide shows a simple way to do it with a spreadsheet.
What alt text is for
Alt text is a short written description of an image, added in the code of the page. It has two jobs:
- People who use screen readers. A screen reader reads the alt text aloud. Without it, the person may hear only a file name, or nothing.
- Search. Search engines read alt text to understand an image. It is the smaller reason.
The three cases
- Informative image. It adds meaning to the page. Describe what matters.
- Decorative image. It is only for looks, like a line or a pattern. Use an empty alt, written as
alt="". The screen reader then skips it. - Functional image. The image is a link or a button. Describe what happens when you click, not what you see. For example, a magnifying glass icon in a button should say "Search".
The W3C alt decision tree is a yes/no question guide. It helps you choose between describing the meaning, describing the function, using an empty alt for decoration, or repeating complex information elsewhere on the page.
Good and bad alt text (fictional examples)
These examples are made up for a fictional shop that sells ceramic mugs.
| Image | Bad alt | Better alt | Why |
|---|---|---|---|
| Blue mug on a product page | mug |
Blue ceramic mug with a wide handle |
Says what a buyer needs to know |
| Photo of the maker at a wheel, on the About page | image of potter pottery clay wheel best mugs buy |
Our potter shaping a mug on the wheel |
No keyword stuffing, no "image of" |
| A thin decorative line between sections | line |
alt="" |
Decoration is skipped |
| Cart icon that links to the basket | cart icon |
View basket |
Describes the action |
A bulk method with a spreadsheet
One row per image.
| Column | What to write |
|---|---|
| File name | The exact name, so you can find the image later |
| Page context | What is on the page around it: the product name, the heading, the paragraph |
| What the image shows | A plain description. Type it, or draft with a chatbot |
| Draft alt | The AI draft |
| Checked alt | Your final line, after reading it |
Keep "checked alt" separate, so you know which lines a human approved.
Prompt 1: for a chatbot that can see images
Some chatbots accept image uploads. Read the tool's privacy page first, and do not upload photos of people or private things you do not want to share.
I will upload an image from a [type of page, e.g. product page] about [topic].
The text around it says: [paste the nearby heading or sentence].
Write alt text in one sentence, under about 125 characters.
Say what matters on THIS page. Do not add keywords that are not visible.
If the image is only decoration, write: EMPTY.
Prompt 2: when you only paste text descriptions
If your chatbot cannot see images, or you prefer not to upload them, write a short plain description yourself and paste it with the context.
Below is a table. Each row has: file name, page context, and my plain description of the image.
For each row write one alt text, under about 125 characters, in simple English.
Rules: no "image of", no keyword stuffing, only use facts in my description,
write EMPTY for decoration, and for links or buttons describe the action.
Return a table with: file name, alt text.
[paste rows]
The rules
- Length. Under about 125 characters is a common habit, not a strict rule. Keep it short.
- No "image of" or "photo of". The screen reader already says it is an image.
- Do not stuff keywords. One natural product name is fine. A list of search words is not.
- Say what matters on this page. The same photo of a mug may need different alt text on a product page and on a blog post about a workshop.
- Check every line yourself. AI can misread an image. It may confuse colours, count things wrongly, or invent a detail. Never publish a draft without reading it next to the image.
Real-world example: For my own blog, an AI once described a simple black coffee mug as "a vibrant, multi-colored ceramic mug with a floral pattern" just because of a tricky shadow. I had to manually correct it to "Black ceramic mug on a wooden desk". Always verify colors, text, and object counts yourself!
Worked example: a shop's product images (fictional)
A fictional shop has three photos of the same blue mug. The photos show the front, the handle close-up, and a hand holding it.
The owner fills the sheet. For the front view, the AI draft says "A mug". The owner sees that is too short and writes "Blue ceramic mug, front view". For the handle, the AI says "Blue mug with a decorative handle", but the handle is plain. The owner fixes it to "Close-up of the mug's wide, smooth handle". For the hand photo, the AI says "Person holding a mug and smiling", but no face is shown. The owner writes "Hand holding the blue mug to show its size". Each line is different, and each is true.
For the product text around these images, see AI product description generators.
How to apply the alt text in bulk
On a simple site, you have two normal ways:
- Edit the HTML. Find each
<img>tag and add or change thealt="..."part. Work from your sheet, row by row. - Use your page builder. Most page builders have a field called alt text or image description for each image. Check your builder's help pages for where it is.
After you finish, open 5 pages and check them.
For more on images and search, read about AI tools for blog SEO images. If you also need to make the pictures themselves, see AI tools for blog images.
Fix list: bad drafts and what to do
| If the AI draft is... | Do this |
|---|---|
| Too long | Ask for one short sentence, or cut it yourself |
| Starting with "Image of" | Delete those words |
| Full of search words | Rewrite with one natural description |
| Wrong about colour, text or number of objects | Correct it by looking at the image |
| Describing a decorative image | Change to an empty alt |
When not to use AI for alt text:
Do not use AI alone for charts, diagrams, maps or screenshots with important text. These need exact information, and the AI may get it wrong. For a chart, write a short alt and put the full data in text on the page. With five images, write them yourself.