UtilibyWritten by the Utiliby editorial team · Last updated October 13, 2026 · Rules and formulas reviewed October 2026
What this free alt text checker does
Alt text is the written alternative to an image. It lets people who cannot see the image, including blind and low-vision people who use screen readers or braille displays, get the same information as everyone else. It also appears when an image fails to load, and search engines read it to understand the picture. This free online alt text checker reviews your description against the practical rules that accessibility guidance and experienced writers use, scores it from 0 to 100 and tells you exactly what to fix.
You choose the image type (informative, functional, decorative, chart or diagram, or image of text), paste your alt text and optionally add the caption or nearby text. The tool flags a missing or empty alt, prefixes such as image of, file names, generic words, descriptions that are too short or too long, keyword stuffing, web addresses and HTML, all capital letters, emoji and text that only repeats the caption. A screen reader preview shows how the image would be announced, and a length gauge shows where you sit against the recommended limit. A second tab checks a whole page at once, and a guide tab shows good and bad examples for each image type.
How to check your alt text
- Pick the image type. Ask what the image is for on this page. A decorative flourish needs an empty alt. A button icon needs the action.
- Paste your alt text. Leave it empty to see how a missing alt is reported.
- Add context (optional). Paste the caption or the sentence next to the image so the tool can spot repetition.
- Read the score and the checks. Fix each flagged item. Every check has a short explanation of why it matters.
- Listen to the preview. Read the screen reader line aloud. If it sounds awkward or repeats the page, rewrite it.
- Check the whole page. Paste your HTML into the Check a page tab to audit every image in one go.
Alt text for each type of image
| Image type | What the alt should do | Example |
|---|---|---|
| Informative | Convey the information the image adds to the page | Golden retriever catching a red frisbee on a beach. |
| Functional | Describe the action or destination | Search |
| Decorative | Be empty so it is skipped | alt="" |
| Chart or diagram | Name it and state the key point; put the data in text nearby | Bar chart: online sales doubled from 2022 to 2025. Data table follows. |
| Image of text or logo | Repeat the text exactly | Utiliby |
The right answer for the same picture can change from page to page. A photo of a lighthouse on a travel page might be described fully, while the same photo used as a faint page background is decorative.
The rules this checker applies
- Missing alt. Without an alt attribute, many screen readers read the file name aloud. This is the most serious error.
- Redundant prefixes. Words like image of, picture of and photo of repeat what the screen reader already announces.
- File names. Text such as IMG_2041.jpg is meaningless to a listener.
- Generic words. Alt text that is only photo, image, banner or graphic says nothing about the content.
- Too short or too long. A single word rarely carries enough meaning. Very long strings are tiring to hear and can be truncated by tools.
- Keyword stuffing. Repeating words hurts both listeners and search quality.
- URLs and HTML. They are read character by character and are never useful.
- All capital letters and emoji. Some screen readers spell capitals out or read emoji names in a distracting way.
- Repeating the caption. If the visible caption already says it, the alt should add something new or be left empty.
- Wrong approach for the type. Functional images should describe the action rather than the picture, and decorative images should have empty alt.
How to write alt text that works
Start with the purpose. Imagine reading the page aloud to a friend over the phone: what would you say about this image so that they understand the page as well as you do? That is your alt text. Describe the most important thing first, because listeners can skip ahead and some tools shorten long strings. Use the same tone as the surrounding text, and write complete, natural phrases rather than lists of tags.
Be specific. Dog says little. Golden retriever leaping to catch a red frisbee on a sunny beach says a lot, in about ten words. Include text that appears in the image, relevant emotion or action, and anything that the surrounding text relies on. Leave out details that do not matter to the page. For people, describe what is relevant to the context and avoid guessing at age, identity or feelings that are not stated.
Do not repeat information that sits right beside the image. If a caption says Maria Lopez accepts the award, the alt text can describe what is not in the caption, or can be kept very brief. Do not use the alt attribute to hold a long essay; if an image needs a lot of explanation, place it in visible text near the image so that everyone can read it.
Charts, diagrams, maps and infographics
Complex images carry more information than a short phrase can hold. The accepted pattern is a two-part approach. First, give a short alt text that identifies what the image is and, for a chart, states the main finding. Second, provide the full information in text on the page, such as a data table under a chart or a step-by-step description beside a flow diagram. This serves screen reader users, people who zoom in heavily, and anyone who prefers to read the numbers. Do not rely on color alone in the visual and describe key relationships in words. This tool allows a longer limit of about 250 characters for charts and diagrams, but a data table is still better than a long alt.
Links, buttons and icons
When an image is the only content of a link or a button, its alt text is that control's accessible name. It should describe what happens when activated, not what the icon looks like. A shopping cart icon in a button should say View cart, not Shopping cart icon. A logo that links to the home page should say something like Utiliby home. If an image sits next to link text that already says the same thing, the image is redundant and should have an empty alt so the link is not announced twice.
Alt text and SEO
Search engines use alt text, together with the file name, surrounding text and page title, to understand what an image is about. It is also the text shown for image search results in some contexts. The same advice applies as for accessibility: describe the image accurately and naturally. Including a relevant term where it genuinely fits can help, but stuffing keywords makes the experience worse for listeners and offers no reliable benefit. Good alt text for people is the best alt text for search.
Alt text and WCAG
The main requirement is WCAG Success Criterion 1.1.1 Non-text Content (Level A): all non-text content that is presented to the user must have a text alternative that serves the equivalent purpose, with exceptions for decorative content, controls, time-based media, tests, sensory experiences, CAPTCHA and content only for presentation. Related criteria include 1.4.5 Images of Text, 2.4.4 Link Purpose (In Context) and 4.1.2 Name, Role, Value for image controls. Laws such as the ADA, Section 508 and the European Accessibility Act point to WCAG, so missing alt text is one of the most common reasons for accessibility complaints and failed audits.
Common alt text mistakes
- Leaving the alt attribute off, or filling every image with the page title.
- Using the file name or a CMS default.
- Starting every description with image of.
- Writing a paragraph in the alt attribute.
- Describing a button icon rather than its action.
- Adding alt text to purely decorative images instead of leaving it empty.
- Repeating the caption word for word.
- Trusting an automatic description without reading it.
What this tool cannot do
It cannot see or understand your image, so it cannot confirm that your description is correct or complete. It does not know how the image is used in your page unless you tell it. It cannot judge tone, cultural context or the sensitivity of a description. The score reflects patterns that are usually signs of weak alt text, but a perfect score on a wrong description is still wrong. Always read your alt text with the image in front of you, and for important content, try it with a screen reader such as NVDA, JAWS, VoiceOver or TalkBack.
Privacy
All checking happens in your browser. The text and HTML you paste are never uploaded, logged or stored. Reload the page and they are gone, so copy or download your report before you leave.
Frequently asked questions
What is alt text?
Alt text is the text alternative of an image, written in the alt attribute of the img element. Screen readers read it aloud, braille displays show it, and browsers show it when the image fails to load. Search engines also use it to understand the image.
What makes good alt text?
It conveys the same information or function as the image in the page's context, in a short natural phrase or one or two sentences. It leaves out the words image or photo, does not repeat nearby text and does not stuff keywords.
How long should alt text be?
Aim for under about 125 characters for most images, which is a common practical limit because some screen readers and tools split or truncate long strings. Charts and diagrams can need more, which is best placed in a visible long description with a short alt.
Should alt text start with image of or photo of?
No. Screen readers already announce that the element is an image, so the prefix is repeated noise. Include the medium only when it matters, for example a painting, a pencil sketch or an X-ray.
What is decorative alt text?
A decorative image adds no information, such as a divider or a purely visual flourish. Give it an empty alt attribute, alt="", so assistive technology skips it. Do not omit the attribute, because then some screen readers read the file name.
What alt text should a linked image or button have?
Describe where the link goes or what the button does, not what the image looks like. A magnifying glass icon in a search button should be labeled Search. A logo that links home can be labeled Company name home page.
How do I write alt text for a chart or graph?
Write a short alt that names the chart and states its main takeaway, then give the full data in a visible table or a text description near the chart. The alt text alone is not enough for the detail.
How do I write alt text for an image of text?
Repeat the text exactly. Avoid images of text where you can, since real text scales, reflows and can be restyled. A logo's alt text is normally the company name.
Is it okay to use keywords in alt text?
Only where they describe the image naturally. Lists of keywords are poor for people using screen readers and are treated as spam by search engines. Write for the person first.
Does this checker look at my image?
No. It is rule-based and checks only the text you provide, plus the image type and optional caption. It cannot judge whether the description is true, so you must review that yourself.
What do the scores mean?
The score starts at 100 and loses points for each problem found, such as a file name, a generic word, a redundant prefix or excessive length. 85 and above is good, 60 to 84 needs a look, and below 60 needs work. It is a guide, not a certification.
Can I check the alt text of a whole web page?
Yes. Use the Check a page tab and paste your HTML, or one alt text per line. The tool lists every img element with its alt text, verdict and issues, and flags missing alt attributes.
What is the difference between a missing alt and an empty alt?
A missing alt attribute is an error because assistive technology may read the file name. An empty alt, alt="", is a deliberate statement that the image is decorative and is correct for those images.
How does alt text relate to WCAG?
It supports Success Criterion 1.1.1 Non-text Content at Level A, which requires text alternatives for non-text content, with exceptions such as decorative images. Related criteria include 1.4.5 Images of Text and 2.4.4 Link Purpose.
What should I do with alt text for social media or email?
The same principles apply. Many platforms have a separate field for it. Email clients may block images by default, so alt text is also what many recipients see first.
Can AI write my alt text?
AI tools can draft descriptions, but they often miss context, purpose and sensitive details, and can be confidently wrong. Use a draft as a starting point, edit it for the image's role on your page and check the result with this tool.
What can I print or save?
Print / save as PDF, CSV and Copy summary work on the tab you are viewing. The printout contains only the report for that tab.
Sources and further reading
- W3C WCAG 2.2, Success Criterion 1.1.1 Non-text Content, and Understanding SC 1.1.1, for the text alternative requirement.
- W3C Web Accessibility Initiative, Images Tutorial (decorative, informative, functional, text and complex images).
- WHATWG HTML Living Standard, the img element and Requirements for providing text to act as an alternative for images.
- W3C WAI-ARIA Authoring Practices and Accessible Name and Description Computation, for how alt text becomes an accessible name.
- WebAIM, Alternative Text, for practical guidance on writing and testing alt text.
Sources were consulted in October 2026. Standards and rules can change, so always check the official page for your situation.