AI Alt Text Generator
Generate descriptive, concise, and detailed alt text for any image. No API key needed.
Drop an image here or click to select
Alt Text Generator Features
Browser-based image analysis for accessibility and SEO.
Get descriptive, concise, and detailed versions to choose from.
Fully client-side analysis using Canvas API. No external service needed.
Your image stays in your browser. The workflow runs locally.
Key Takeaways
- Your image stays on your device - it is read and analyzed entirely in your browser on a canvas, with nothing uploaded to a server.
- The tool measures visual properties like dominant color, lighting, contrast, orientation, and pixel dimensions; it does not recognize objects or read text, so it cannot name the actual subject on its own.
- Always fill in the Image Context field with the real subject (for example red running shoe on white background), since that text is what makes every generated variant accurate.
- It always produces three variants - use Concise for icons and decorative images, Descriptive for most blog and product photos, and Detailed for charts or complex visuals - then edit before publishing.
How to Generate Alt Text for an Image
Load your image
Drag an image onto the drop zone or click Select Image to choose a file. The image is read and rendered locally in your browser, then sampled on a canvas to measure its dominant color, lighting, contrast, orientation, and pixel dimensions. Nothing is uploaded to a server.
Add context and pick a tone
Type a short note in the Image Context field, such as product photo or team headshot, to make the wording more specific. Set the Primary Tone to Descriptive, Concise, or Detailed to control which variant is shown first; all three are always produced.
Generate and copy
Click Generate Alt Text to build three description variants from the analysis and your context. Review each one, click Copy on the version that fits, and paste it into the alt attribute of your HTML img tag. Use Try Another Image to start over.
What the Tool Reads From Your Image
This generator does not recognize objects or read text in a photo. Instead it samples a downscaled copy of your image on a canvas and measures a small set of visual properties, then phrases them into alt text. The table below shows each property, how it is derived, and the values it can report.
| Property | How it is measured | Possible values |
|---|---|---|
| Dominant color | Average red, green, and blue across sampled pixels | red, green, blue, yellow, orange, purple, white, gray, black, colorful |
| Lighting | Overall average brightness of the image | bright, well-lit, low-light |
| Contrast | Share of very bright versus very dark pixels | high contrast, soft contrast |
| Orientation | Width-to-height aspect ratio | landscape, portrait, square |
| Dimensions | Natural pixel width and height of the file | shown as width x height px |
| Context | Optional text you type in the context field | inserted directly into each variant |
Which Variant Should You Use
Concise for decorative images
The Concise variant keeps wording short, naming color and orientation with your context. It suits icons, thumbnails, and supporting visuals where a brief label is enough for a screen reader.
Descriptive for most content
The Descriptive variant adds lighting and contrast around the subject. It is the balanced default for blog images, product shots, and articles where the picture carries meaning.
Detailed for complex visuals
The Detailed variant combines orientation, lighting, contrast, color, and dimensions in one sentence. Use it as a fuller starting draft for charts, infographics, or layered scenes.
Always add context
Because the tool reads visual properties and not subject matter, the context field is what makes alt text accurate. Name the actual subject so every variant describes the real image, then edit before publishing.
Common Problems and Fixes
The description does not mention the subject
The tool measures color, brightness, and shape, not what is pictured. Type the subject into the Image Context field, for example red running shoe on white background, and generate again so each variant includes it.
Dominant color is reported as colorful
When no single channel clearly leads, the analysis labels the image colorful and drops the color prefix. This is expected for busy or multi-color photos; lean on the context field for specificity instead.
Nothing happens when I drop a file
The drop zone only accepts image files such as JPEG, PNG, WebP, GIF, and BMP. Drop a single image at a time. If it still does not load, use the Select Image button to pick the file directly.
The Copy button did not work
Copying uses the browser clipboard, which some browsers block on non-secure pages or without a user gesture. Make sure you are on the https page and click Copy directly, or select the text and copy it manually.
About AI Alt Text Generator
This free tool analyzes image properties like colors, brightness, and dimensions to generate three alt text variants for use in HTML img tags.
Frequently Asked Questions
Is this tool free to use?
Yes, this tool is completely free.
No account or registration is required.
You can use it as many times as you like.
Is my image data private?
All analysis happens in your browser.
Your image is never sent to any server.
We do not store, log, or share your images.
How accurate are the generated descriptions?
The tool analyzes color, brightness, and dimensions for basic descriptions.
Adding context in the context field significantly improves relevance.
Always review and adjust the output for production use.
Can I edit the generated alt text?
The generated text is a starting point.
Copy it and customize it to better describe your image.
Good alt text is specific to the image context and purpose.
Does it work on mobile?
Yes, the tool is fully responsive.
It works on phones, tablets, and desktops.
No app download is needed.
Can I use the output commercially?
Yes, there are no restrictions on usage.
The output belongs entirely to you.
Use it for personal or commercial projects freely.
What browsers are supported?
All modern browsers are supported.
This includes Chrome, Firefox, Safari, and Edge.
Keep your browser updated for best results.
What is the tone selector for?
The tone selector sets which variant appears first in the results.
All three variants (descriptive, concise, detailed) are always generated.
Choose based on your primary use case.
Works in Chrome, Firefox, Safari, Edge, Opera, and other modern browsers on Windows, macOS, Linux, Android, and iOS. No software installation or sign-up required. All conversions run directly in your browser, so your files never leave your device and are never uploaded to a server. Free to use with no account needed.
Sources and References
Format and tool details on this page are based on the official specifications and documentation below.
- WCAG: Text Alternatives- W3C
- alt text / img accessibility- MDN Web Docs