Menu
By the ImageSEO Team. Updated October 2026.
Short answer: Yoast SEO checks your images but does not write anything for them. It runs an image keyphrase check on each post, lists your images inside its XML sitemaps, and uses an image for your social previews and schema. It does not write alt text, rename image files, add captions or compress images. Yoast’s AI features cover titles, meta descriptions, summaries and content suggestions, and none of them generates alt text. So on a Yoast site, the alt text is still yours to write, by hand or with a separate tool.
Below is what each Yoast image feature really does, how to check it on your own site, the problems people run into most, and how to fill the gap.
| Feature | What it does | What it doesn’t do |
|---|---|---|
| Image keyphrase check (SEO analysis) | Checks whether the post has images and whether their alt text contains your focus keyphrase | Doesn’t write or fix the alt text |
| Images in XML sitemaps | Adds the images found in each post’s content to that post’s sitemap entry | Can miss images that page builders or other plugins add outside the content area |
| Social previews (Open Graph) | Uses the featured image, or an image you choose in the Social tab, for og:image |
Doesn’t resize, crop or design the image |
| Schema | Includes the page’s main image in its structured data graph | Doesn’t describe the image |
| Yoast AI (Premium) | Generates titles and meta descriptions, summaries and optimisation suggestions | No alt text, captions or file names |
The check sits in Yoast’s SEO analysis next to your focus keyphrase. According to Yoast’s own explanation, it does two things: it checks that the post has images, and it checks how many of their alt texts contain the keyphrase.
Two things to keep in mind. First, a green bullet means the keyphrase is present, not that the alt text is good. “Hiking boots hiking boots” passes as well as “Brown leather hiking boots on a rocky trail”. Second, chasing the bullet can push you into writing the keyphrase into images where it doesn’t belong. Write alt text that describes the image, and use the keyphrase only where the image really shows it. Google itself warns that keyword-stuffed alt attributes “may cause your site to be seen as spam”.
Yoast’s sitemaps list your posts and pages. Yoast says that if those pages contain images, it includes information about them in the page’s sitemap entry. There is no separate image sitemap file.
How to check it: open yoursite.com/sitemap_index.xml, click your post sitemap and look at the Images column. It shows how many images Yoast found for each URL.
If the count is zero or too low: Yoast detects images in the standard WordPress content area and in builders that are compatible with its analysis. Images placed by sliders, galleries or some page builders can be missed. Developers can add them with Yoast’s sitemap filters, for example wpseo_sitemap_urlimages. Also remember that Google can find images on a crawled page without any sitemap. A sitemap mainly helps with images Google might otherwise not discover. Our image sitemap guide explains when that is.
For Facebook, LinkedIn and X previews, Yoast outputs an og:image. By default that is the post’s featured image. In the Social tab of the Yoast box you can set a different image for one post, and in Yoast’s settings you can choose a site-wide fallback image for pages that have none.
og:image for Discover.This is where most WordPress sites fall behind. Yoast tells you something is missing, but somebody still has to write:
image1.jpg.They do different jobs and run side by side without conflict in normal use. Yoast handles titles, meta descriptions, sitemaps, schema and the checks. ImageSEO writes the image text that Yoast checks for:
Once alt text exists, review the images on your most important pages and add your keyphrase where the image really shows it. That is the part no tool can judge for you, and it is what turns Yoast’s bullet green for the right reason. The plugin is free for 10 images a month on WordPress.org, and you can test one image without installing anything in our free alt text generator.
No. Yoast checks whether images have alt text containing your keyphrase. Its AI features generate titles, meta descriptions, summaries and suggestions, not alt text.
Not as a separate file. It adds the images it finds in each post to that post’s entry in the XML sitemap. You can see the count in the Images column of your post sitemap.
Usually because the images are added by a slider, gallery or page builder outside the content area Yoast analyses. The images can still be fine for Google; the check just doesn’t see them.
For posts with more than four images, Yoast gives green when 30% to 70% of the alt texts contain it, and orange above 70%.
The featured image by default. You can override it per post in the Social tab, and set a fallback image for the whole site in Yoast’s settings.
For writing alt text and file names, and for compression, yes. Yoast covers checks, sitemaps, schema and social tags, but not the image text itself.
