The Audit That Passes and the Page That Doesn't
Run an automated accessibility check on your site. Zero missing alt attributes. Clean report.
Now have someone use it with a screen reader. The product listing announces "image image image image." The chart is described as "chart.png." The team page reads out "photo of a person smiling" eleven times in a row.
Every image has an alt attribute. Every one of them is useless.
Automated checking can verify that alt text exists. It cannot verify that alt text helps — and the gap between those two things is where most real accessibility failures live.
What a Checker Can and Can't Tell You
The Image Alt Checker scans a page and reports the alt attribute on every image:
- Enter the page URL.
- Review each image and its alt text.
- Identify missing attributes and empty ones.
That output answers the mechanical questions:
- Which images have no alt attribute at all?
- Which have
alt=""? - What does each one say?
What it can't answer is whether the text conveys what the image conveys. That requires reading each one and asking a question no tool can ask: if this image failed to load, would this sentence make the page work?
The efficient workflow is to use the tool to get the inventory, then apply judgement to the list. Reading thirty alt texts in a list takes five minutes. Finding them by inspecting a page one image at a time takes an hour.
Patterns That Pass Automated Checks and Fail Users
Filename alt text
<img src="IMG_4471.jpg" alt="IMG_4471.jpg">
Present, non-empty, entirely useless. Frequently generated by CMS systems that populate alt from filename by default.
Signal to look for: alt text containing a file extension, a camera prefix, or a long numeric string.
Redundant prefixes
<img alt="Image of a woman using a laptop">
<img alt="Photo showing the new office building">
<img alt="Graphic of the sales process">
Screen readers already announce that the element is an image. Adding "image of" produces "image, image of a woman using a laptop."
Fix: Start with the content. alt="A woman using a laptop at a kitchen table".
The exception is when the medium matters — a painting, a historical photograph, a diagram versus a photograph of the same thing. alt="Oil painting of Rotterdam harbour, 1890" is appropriate because the medium is part of the information.
Keyword stuffing
<img alt="cheap flights Berlin cheap flights Munich book flights Europe">
Reads terribly to anyone using a screen reader and hasn't been an effective SEO tactic for many years. It's also increasingly a legal exposure as accessibility regulation tightens.
Signal to look for: alt text with repeated terms, no grammatical structure, or unusual length for what the image shows.
Generic descriptions on distinct images
<img alt="product">
<img alt="product">
<img alt="product">
Common on e-commerce listing pages. Technically present; provides no way to distinguish one item from another.
Fix: Include what makes each one different. alt="Navy wool overcoat, three-quarter length".
Duplicating adjacent text
<h2>Our Amsterdam Office</h2>
<img src="office.jpg" alt="Our Amsterdam Office">
The screen reader announces the heading, then the identical alt text. Redundant.
If the image adds nothing beyond the heading, alt="" is correct. If it shows something specific, describe that: alt="Open-plan office with exposed brick and large windows overlooking a canal".
The same alt on every decorative image
<img src="divider.svg" alt="decorative divider">
Repeated forty times down a page. Decorative images should have alt="", which tells assistive technology to skip them entirely. Describing a decoration is worse than not describing it.
The Decision Framework
For each image, work through this:
1. Does the image convey information not available in surrounding text?
No → alt="". This is the correct answer for decorative images, spacers, and images that duplicate adjacent content.
2. Is the image the only content of a link or button?
Yes → the alt text must describe the destination or action, not the picture. A magnifying glass icon linking to search should be alt="Search", not alt="Magnifying glass".
3. Does the image contain text? Yes → the alt must include that text. An image of a poster, a quote card, or a button graphic needs its words available. Better still, don't put important text in images.
4. Is it a chart, diagram, or complex graphic?
Yes → short alt naming what it is, plus a longer description in the page content or via a linked description. alt="Bar chart of quarterly revenue by region" identifies it; the actual data belongs in text or a table nearby.
5. Everything else → describe what matters about the image in context.
That last phrase is the crux. The right alt text depends on why the image is there. The same photograph of a bicycle needs different alt text on a product page ("Red steel city bicycle with front basket and leather saddle"), a news article about cycling infrastructure ("A bicycle parked against a barrier on a newly widened cycle lane"), and a blog post about a repair ("Rear derailleur with a bent hanger").
Length and Detail
There's no specified maximum, but practical guidance:
Aim for one clear sentence. Roughly 100–150 characters is comfortable for most images.
Longer is fine when warranted. A complex image genuinely needing more description should get it, ideally through a longer description mechanism rather than an enormous alt attribute.
Shorter is fine too. alt="Search" on a search button is complete.
Don't end with a full stop unless it's a complete sentence. Minor, but the pause it introduces in screen reader output is noticeable when it's unnecessary.
Prioritise what matters. A team photo probably doesn't need every person's clothing described. A product photo probably does need the colour and key features.
Auditing Systematically
For a site of any size, work through it as a process:
Extract alt text from your key page templates. Homepage, category page, product page, article page, contact page. Templates repeat, so fixing one fixes hundreds.
Sort the results into categories. Missing attributes, empty attributes, filename text, generic text, and text that looks reasonable.
Handle the mechanical categories first. Missing and filename-derived alt text are unambiguous problems with clear fixes.
Read the "reasonable" ones properly. This is where judgement is needed and where automated tools stop helping.
Check images inside links separately. These have the highest impact — a link with unhelpful alt text is a navigation failure, not just a description gap.
Fix at the source. If your CMS populates alt from filename, change the CMS behaviour. Fixing individual pages while the template keeps generating bad alt text is unending work.
Make alt text a required field in your content workflow, with the option to explicitly mark an image decorative. Requiring a value without a decorative option leads to authors typing "image" to get past validation.
Practical Tips
Test with an actual screen reader occasionally. Fifteen minutes with VoiceOver or NVDA on your own site is more instructive than any checklist.
Read your alt text aloud in page order. Awkwardness and repetition become obvious immediately.
Write alt text when you place the image, while you still know why you chose it.
Don't put important information only in images. Text in an image is inaccessible, untranslatable, and unsearchable.
Remember alt text serves more than screen readers. It displays when images fail to load, helps on slow connections, and is used by search engines.
Consider your legal obligations. Accessibility requirements have tightened in the EU, UK and US, and image descriptions are among the most frequently cited failures.
FAQ
What's the difference between alt="" and no alt attribute?
alt="" tells assistive technology to skip the image. A missing attribute leaves the behaviour undefined — many screen readers fall back to announcing the filename.
Should alt text include keywords? Naturally descriptive text usually includes relevant terms anyway. Deliberately stuffing keywords produces poor descriptions and no meaningful ranking benefit.
How long should alt text be? Usually one sentence. Complex images may need more, ideally via a longer description alongside a short alt.
What about images inside links? Describe the destination or action, not the image. The alt text becomes the link text.
Do decorative images need alt text?
They need alt="" — an empty attribute, not a missing one, and not a description.
Can automated tools check alt text quality? They can flag obvious problems like filenames and empty strings. Whether a description conveys the right information in context requires human judgement.
The Takeaway
Alt text auditing has a mechanical half and a judgement half. Tools handle the first — finding what's missing, empty, or obviously wrong. The second requires reading each description and asking whether it does the job the image does. Getting the inventory quickly is what makes the judgement part feasible.
Check every image alt attribute on any page free with the Image Alt Checker at sadiqbd.com — no sign-up, instant results.
