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By the ImageSEO Team. Updated October 2026.
Short answer: alt text describes what an image shows, for people who can’t see it and for search engines. It is invisible on the page. A caption is visible text under the image that adds context, like who, where or why. The title is the image’s name in your media library; in HTML, a title attribute only shows as a tooltip on mouse hover. A description (in WordPress) is a longer note shown only on the image’s own attachment page, if your site has one. For search, alt text matters most, captions help, and titles and descriptions matter least.
| Field | Who sees it | Where it ends up | Use it for |
|---|---|---|---|
| Alt text | Screen reader users; everyone if the image fails to load; search engines | The alt attribute of the <img> tag |
What the image shows, in one short phrase |
| Caption | Every visitor, under the image | A <figcaption> (or theme caption) next to the image |
Context the photo can’t show: names, place, date, credit |
| Title | You, in the media library; mouse users as a tooltip if added as an attribute | The media item’s name; optionally a title attribute |
Finding the file again; rarely anything on the page |
| Description (WordPress) | Visitors of the attachment page only | The attachment page body | Longer notes, if you use attachment pages at all |
Google’s image documentation says it “extracts information about the subject matter of the image from the content of the page, including captions and image titles”. So captions and titles are not worthless. But Google calls alt text the most important attribute for describing an image, and it is the one screen readers rely on.
This is the pair people mix up most, because both are text about the same image. The difference is the audience:
Example for a photo on a local news page:
<figure>
<img src="harbour-road-warehouse-fire.jpg"
alt="Firefighters spraying water on a burning warehouse roof at night">
<figcaption>The fire on Harbour Road took six hours to control. Photo: Jane Doe</figcaption>
</figure>
Don’t paste the caption into the alt text. A screen reader announces both, so the listener would hear the same sentence twice. If the caption already describes the image fully, keep the alt text short and focused on what is visible.
Two different things share the name “title”:
title attribute. Optional HTML that shows a tooltip when a mouse hovers over the image. Touch screens don’t show it, and screen readers don’t treat it as a replacement for alt text.So the title never does the job of alt text. A clean media title helps you find files later; give it real words instead of IMG_4921. Only add a title attribute if the tooltip really helps your visitors.
Open any image in Media → Library and you will see Alt Text, Title, Caption and Description. Three behaviours catch people out:
When you insert an image into a post with the block editor, WordPress copies the library’s alt text into that image block. From then on, the alt text belongs to that block. WordPress core treats this as intended: the same image can need different alt text in different articles. If you later fix the alt text in the Media Library, posts that already contain the image keep the old text. New insertions use the new text.
What to do: write alt text when you upload, before the image goes into a post. For older posts, open the image block and edit its alt text in the block settings.
The library caption becomes the default caption of the image block when you insert it. After that, you can edit the caption in the post without touching the library.
Each upload can have its own attachment page, which shows the description. Since WordPress 6.4, new sites have attachment pages turned off by default, and the attachment URL goes to the file instead. On those sites, the description is effectively a private note.
my-new-black-kitten.jpg is its own example of a good one.alt="" for purely decorative images.How often do sites skip the first two? In our crawl of the Tranco top 10,000 homepages, 11.3% of 306,634 images had no alt attribute at all (July 2026), and only 46.4% of 285,438 file names were descriptive words (August 2026). See the alt text study for the method.
The ImageSEO plugin can write alt text, titles, captions and descriptive file names when you upload an image, and fill them in bulk for images already in your library. Because WordPress copies alt text into a post when you insert the image, the on-upload setting is the one that matters most: the alt text exists before anyone places the image. When the plugin renames a file, it also updates links to that file inside your posts. Try one image for free in our alt text generator, or install the plugin from WordPress.org (10 images a month free).
For the HTML side of the same topic, including figcaption markup and file names, see our guide to image alt, title, file name and figcaption.
No. Alt text says what the image shows; the caption adds context. Screen readers announce both, so identical text is read twice.
A little. Google says it uses captions and image titles from the page as context. Alt text, the file name and the surrounding text matter more.
No. Screen readers rely on alt text. A title attribute only adds a mouse tooltip, which touch users never see.
It is shown on the image’s attachment page. On sites where attachment pages are off, the default for new sites since WordPress 6.4, visitors never see it.
Because the block editor stored the old alt text in the post when you inserted the image. Edit the alt text in the image block of that post.
