Image alt text checker
Find the images on a page that screen readers can’t describe, and how to fix them. Free, with no sign-up.
Alt text: a plain-English guide
37 Digital’s free image alt text checker reads one web page, or HTML you paste in, and lists the images, image links and icon buttons a screen reader can’t describe, with plain-English fixes for website owners. Alt text is the short description screen readers read aloud in place of an image. The Web Content Accessibility Guidelines (WCAG 2.2), the international standard accessibility audits measure against, require a text alternative for every image that conveys meaning, even at their most basic level, Level A (success criterion 1.1.1 Non-text Content).
What is alt text?
Alt text – short for alternative text – is a written description of an image, stored in the page’s HTML as the image’s alt attribute. Screen readers read it aloud for blind and partially sighted visitors, browsers show it when an image doesn’t load, and search engines use it to understand what the image shows.
It’s often missing: WebAIM’s 2026 study of the top million home pages found images with missing alt text on 53.1% of them.
How do you write good alt text?
Describe what the image shows that matters on this page – what you’d say if you were reading the page to someone over the phone.
- Skip “image of” and “photo of” – screen readers already say it’s an image.
- Include any words in the image, such as the text on an offer banner.
- Don’t repeat the text beside it, and don’t stuff it with keywords.
- Never use the file name. “IMG_4021” tells nobody anything.
Context matters too: on a bakery’s menu page, a photo might be “Sourdough loaf with a crackly crust”; on its careers page, “Our head baker shaping the bread”.
What to write also depends on what the image does, as the W3C’s alt decision tree shows:
| Type of image | Example | What to write |
|---|---|---|
| Informative | A product photo | What matters: “Oak dining table with six chairs” |
| Image of text | An offer banner | The words: “Spring sale – 20% off garden furniture” |
| Decorative | A divider or background pattern | Empty alt text, alt="" |
| Linked image or logo | Your logo, linking to your home page | Where the link goes: “Brightside Bakery – home” |
| Image button | A magnifying glass on a search button | What it does: “Search” |
| Complex image | A chart or diagram | Its main point, with the detail in the page text – a two-part text alternative |
How long should alt text be?
Usually a phrase or one sentence. WCAG sets no character limit, but long alt text is hard to listen to, and screen reader users can’t skim it. This checker notes alt text over about 150 characters, as a suggestion rather than a fault. Shopify, for example, allows up to 512 characters for product media but recommends 125 or fewer. Put any longer explanation in a caption or the page text.
Should decorative images have alt text?
They need empty alt text, not a description. Give purely decorative images, such as dividers and background patterns, alt="" – nothing between the quotes, not even a space – and screen readers skip them.
Leaving the alt attribute out isn’t the same: as the W3C’s guidance on decorative images warns, some screen readers then read out the file name. That’s why this checker fails a missing alt attribute (except on tiny tracking or spacer images, which get a Note) but only asks you to confirm empty ones. Never mark an image as decorative if it shows something people need, or if it’s the only thing in a link.
What alt text should a linked image or logo have?
Alt text that says where the link goes, not what the picture looks like. When an image is the only thing inside a link or button, its alt text becomes the link’s or button’s name: “Brightside Bakery on Instagram”, not “Instagram logo”. If the link also has visible text, the image can have empty alt text. Icons drawn as SVG have no alt attribute, so give the link or button an aria-label instead.
WCAG requires a link’s purpose to be clear (success criterion 2.4.4) and every link and button to have a name (4.1.2), both at Level A. WebAIM’s 2026 study found that 45% of the images missing alt text were linked images.
How do I add alt text in WordPress, Squarespace, Wix or Shopify?
Each lets you set it in the image’s settings, but the field’s name and where you find it differ.
WordPress
In the block editor, select the image and fill in Alternative text in the block settings, or tick Mark as decorative if your version has it. Alt text set in the block applies only to that page or post; alt text in the Media Library is the default each time you insert the image. See WordPress’s Image block guide.
Squarespace
For an image block, use the Image alt text field on the Content tab. Most other images use a related field instead, such as a gallery image’s title, and Squarespace’s alt text guide lists each one.
Wix
Click the image, click the Settings icon and fill in “What’s in the image?”. Wix’s image accessibility guide covers galleries and decorative images.
Shopify
For a product image, open the product in your admin, click the image and choose Add alt text. For a theme image, such as a home page banner, go to Online Store, click Edit theme, then select the section and click Edit on the image (Shopify’s guide).
Whichever you use, publish or save your changes and clear any page cache before checking again. If this checker still flags an image you’ve fixed, the theme may not be using the alt text you set.
Is alt text a legal requirement in the UK?
For most public sector websites, effectively yes. For businesses, the law sets a general duty rather than a checklist.
- Businesses and charities. The Equality Act 2010 requires anyone providing a service to the public to make reasonable adjustments so disabled people aren’t put at a substantial disadvantage (section 20 and section 29). It doesn’t name WCAG or any technical standard. Northern Ireland has the Disability Discrimination Act 1995 instead.
- Public sector bodies. Unless they’re exempt, the Public Sector Bodies (Websites and Mobile Applications) (No. 2) Accessibility Regulations 2018 require their websites to be accessible and to carry an accessibility statement. The government’s guidance says a site meets the legal requirements if it meets WCAG 2.2 at Level AA and publishes that statement. Some charities, such as those mostly funded by public money, are covered too.
- Selling to the EU. The European Accessibility Act (Directive (EU) 2019/882) covers e-commerce services provided to consumers after 28 June 2025, though microenterprises providing services are exempt – those with fewer than 10 staff and an annual turnover or balance sheet of no more than €2 million. If you sell online to EU consumers, check whether it covers you.
This is general information, not legal advice.
Reading your results
- Fail – a screen reader has nothing useful to read: an image with no alt attribute or other label, alt text that’s only a space, or a link or button whose only content is an image or icon with no name.
- Warning – there’s alt text, but it’s a file name such as “IMG_1234”, or a placeholder such as “image” or “photo of…”.
- Note – worth a look: images marked as decorative, to confirm they are; alt text over about 150 characters; and tracking or spacer images with no alt text.
- Pass – the image has a text alternative, with nothing to fix.
The checker can’t judge whether your alt text describes its image well, read text inside images, or see images set as CSS backgrounds. Sites built as JavaScript apps add their images in the browser, where it can’t see them, so it says so rather than passing the page – paste the HTML your browser shows instead.
Common questions
Does alt text help SEO?
Yes. Google says it uses alt text, with computer vision and the page’s content, to understand images, and that alt text on a linked image is useful as anchor text. Its image SEO guidance warns that stuffing alt text with keywords may get your site seen as spam.
Can AI write my alt text?
It can give you a first draft. AI tools can describe what’s in a photo, but often not why it’s on your page, whether it’s decorative or where a linked image goes, and they can get details wrong. Check each one against the page.
Does the checker test my whole site?
No. It checks one page at a time and doesn’t follow links. Start with your home page, then one page of each type, such as a product page or a blog post. Each connection can run 15 checks a day.
What do you keep when I run a check?
Not your results. Pasted HTML is checked in memory and never stored or logged. For 7 days we keep a short log of each check: the tool, the domain, the outcome, how long it took and a code for your connection that changes daily. We never store your IP address, and the counts behind the daily limits are deleted after 48 hours. Cloudflare, which runs the checker and its Turnstile bot check, does process your IP address. Our privacy policy and About our checker have the details.
We fix alt text and other accessibility issues, and keep new pages in good shape as part of our website maintenance and support. Ask us about accessibility fixes and we’ll take a look.
More free checks
- Email security checker – See whether email from your domain is set up to reach inboxes and stop others sending as you. Checks SPF, DKIM and DMARC.
- Link preview checker – See how your page will look on Google, LinkedIn and Facebook before you share it, and what to fix.
- All our free tools