Image Alt Text Checker: Find Missing and Weak Alt Text
Enter a page address to list every image on it with its alt text — missing, decorative, suspicious or fine — and what a screen reader will announce, with tips for fixing each one.
What the checker looks at
It lists every <img>, image button (<input type="image">), image-map area, inline <svg> and element with role="img" in the page's HTML, and says what a screen reader gets from each:
- Missing — no
altattribute at all. Screen readers may read the file name ("IMG underscore 4 0 2 7 dot jpg"). Always a problem. - Decorative —
alt="". The image is skipped, which is right for decoration — but wrong when the image is the only thing inside a link or button, which then has no name. - Suspicious — alt text that looks like a file name, a placeholder ("image", "photo", "logo"), starts with "image of", runs over 150 characters, or repeats the text right next to it.
- Named — alt text,
aria-labelor an svg<title>that looks like a real description. Only you can judge whether it describes the image well.
The limits of an automatic check
The checker reads the HTML the server sends, so images that scripts add later (some galleries, carousels and apps built entirely in JavaScript) are not seen, and CSS background images are never part of alt text. It can tell that alt text exists and spot common mistakes, but not whether it is accurate: "Dog" on a photo of a cat passes. Use the list as a starting point for reading your page with a screen reader.
Writing good alt text
Ask what the image adds to the page, and write that. The W3C alt decision tree sorts most cases:
- Informative images (a product photo, a portrait in an article): a short description of what matters — "Blue linen shirt, front view".
- Functional images (a logo link, an icon button): the action or destination — "Home", "Search", "Download the PDF".
- Images of text: the same words as in the image.
- Complex images (charts, maps, diagrams): a short alt that names it, and the full data or description in the page.
- Decorative images:
alt="". For inline SVG icons next to a text label, addaria-hidden="true".
Alt text is required by WCAG 2.2 success criterion 1.1.1; the W3C images tutorial has examples for each kind. It also helps search engines understand images — Google uses alt text together with the page's content for image search.
Mobile notes
On phones, VoiceOver (iPhone) and TalkBack (Android) users move through a page one element at a time with swipes, so every unnamed image link costs them a guess and every redundant alt text costs an extra swipe. Alt text also appears when images fail to load on a slow mobile connection or when data saving is on. Keep it short and put the important word first.
Frequently asked questions
When should alt text be empty?
When the image is decorative or its content is already in the text next to it — ornaments, background patterns, an icon beside a word that says the same. Write alt="" (empty, not missing): screen readers then skip the image. A missing alt attribute is different: screen readers may read out the file name.
How long should alt text be?
Usually one short sentence. There is no hard limit, but text over about 150 characters is tiring to listen to and cannot be skimmed; put long descriptions of charts or diagrams in the page text, a caption or a linked description.
Should alt text start with "image of"?
No. Screen readers already announce that it is an image. Start with what matters: "Two-bedroom flat floor plan, 68 m²" rather than "Image of a floor plan".
What alt text does an image link or icon button need?
Alt text that says where the link goes or what the button does, not what the picture looks like: a logo that links home gets alt="Acme home page", a magnifier icon button gets "Search". If the link also has visible text, the image can have alt="".
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