Alt text is one of those small technical details that quietly matters more than it gets credit for. It’s the text a screen reader announces in place of an image for a visually impaired visitor. It’s also what Google Images and other image search tools use to understand what a picture actually shows. An image with no alt text is invisible to both.

Most sites end up with dozens, sometimes hundreds, of images missing it — not out of neglect, but because nobody fills in a field they don’t know exists every time they upload a photo.

How Sanctuary Tiger SEO fixes this

The free plugin includes an Alt Text Fallback feature with two ways it works:

Automatically, on every new upload. The moment an image is added to your Media Library, if it has no alt text at all, the plugin fills it in using the attachment title or filename — cleaned up into readable text. golden-retriever-puppy.jpg becomes “Golden retriever puppy.” Generic camera and screenshot filenames like IMG_4821 or Screenshot 2026-08-01 are detected and given an honest fallback instead of outputting nonsense.

A bulk action for everything already uploaded. In your Media Library, a new “Auto-fill missing alt text” bulk action lets you select existing images and backfill them all at once — useful for a site that’s been running for years with an image library nobody ever went back and fixed.

What it never touches

This is important: the fallback only fills alt text that has never been set at all. If you’ve already written custom alt text for an image — or if you’ve deliberately left an image’s alt text blank because it’s purely decorative, which is a valid and intentional choice in web accessibility — the plugin leaves it alone. It never overwrites anything you or a previous plugin already decided.

A simple fallback, not a replacement for accurate description

To be clear about what this does and doesn’t do: filling in “Golden retriever puppy” from a filename is a reasonable default, but it’s not the same as an actual description of what’s happening in the photo. A truly accurate alt text — “A golden retriever puppy chewing a tennis ball in a backyard” — requires something that can actually look at the image.

That’s what the Pro add-on adds: AI-generated alt text using Claude’s vision capabilities, which looks at the actual picture and writes a real description, along with title, caption, and description fields. If Pro’s AI alt text is active, it simply replaces the free fallback with something more accurate — nothing conflicts between the two.

Here’s what that looks like in the Media Library — all four fields filled in automatically after Pro analyzed the image:

The takeaway

Even the free, filename-based fallback is a meaningful improvement over having nothing at all. A site with alt text on every image — even imperfect, automatically generated alt text — is more accessible and more indexable than one with blank fields scattered across years of uploads.

Get automatic alt text free on WordPress.org →

Frequently Asked Questions

Will this overwrite alt text I’ve already written? No. It only fills in alt text on images where the field has never been set at all — including respecting intentionally blank alt text on decorative images, which is a valid accessibility choice.

Is filename-based alt text actually good, or just better than nothing? It’s a reasonable default, not a true description of the image. For an actual AI-generated description of what’s in the photo, that’s what Pro’s Claude Vision-powered alt text does instead.

Does this affect images already on my site, or only new uploads? Both — new uploads get alt text automatically, and a “Auto-fill missing alt text” bulk action in the Media Library lets you backfill images uploaded before the feature existed.