Find every image missing alt text in Prismic

Every Prismic site we take over has images without alt text. Not a few, usually a lot. Nobody decided to skip it, it just never had a moment: images go in while the pages are being built, the upload screen doesn't ask, and once the site is live nobody opens every document to check.

Why it's worth fixing

• People using screen readers. Without alt text, an image is either skipped or read out as its filename. “aRxg6bpReVYa4nlD underscore JamesBanks dot png” isn't helpful to anyone.
• The law, increasingly. The European Accessibility Act has applied since June 2025, and accessibility audits check alt text first, because it's the easiest thing to spot.
• Search. Alt text is how search engines and AI tools know what an image shows. It's what gets your images into image search, and what an AI summary of your page has to go on.

Where alt text goes missing in Prismic

• Image fields. The normal case. Each one has an alt text box in the document, filled in or not.
• Images inside rich text. A rich text field can hold images too, each with its own alt text. They're easy to miss, because they don't look like a separate field.
• Link to media fields. A link to a file in the media library rather than an image field. There's no alt text box at all, so whatever your site shows comes from your code.

And one catch: an empty alt text box looks the same whether someone forgot it or left it empty on purpose. A background texture should have empty alt text, so screen readers skip it, but in Prismic it looks exactly like a mistake.

See every image without alt text, with Cojack

We built Cojack because there was no way to answer “which images on this site have no alt text?” without opening every document. It reads your whole repository and checks every image in every document.

1. Paste your site's URL into Cojack
2. On the overview, the pages with images missing alt text check shows how many pages are affected and how many images in all
3. Open Assets and click Missing alt text to see every image, with the pages it's on. Sort by Most missing alt to put the images missing it in the most places first
4. Open a document to see its images, and use Only without alt to see just the ones to fix

If you add your write token, Cojack also reads your media library. Then Alt only in library shows images whose alt text is in the library but never reached the page, which has a fix of its own.

Writing alt text that's actually useful

Write what the image is doing on the page, as you'd describe it to someone on the phone. A sentence is usually plenty.

• Skip “image of” and “photo of”. Screen readers already say it's an image.
• Say what matters here. A product shot on a shop page needs the product and colour, the same shot in a blog header might just need the mood.
• Include any text in the image. If a graphic says “50% off this week”, the alt text should too.
• Linked images describe where they go. A logo that links home is “Undefined, home”, not “logo”.
• No keyword stuffing. “Running shoes running shoes best running shoes” helps nobody, search engines included.

A few before and afters:

• “IMG_4521.jpg” → “Three people around a laptop in a bright office”
• “banner” → “50% off all winter coats, this week only”
• “team photo, team, about us, agency team” → “The Undefined team at the 2024 offsite”

How we set up new Prismic projects so it doesn't happen

• Alt text at upload. The one rule we give editors: write the alt text in the media library when you upload, before the image goes in a document. Prismic copies it in when the image is picked.
• Image fields, not link to media. Anything that shows as an image gets an image field, so it has an alt text box.
• Decorative images out of image fields. If an image shouldn't be read out, it's a background in the slice, not an image field that looks like it's missing something.
• A check before launch. We run the site through Cojack before it goes live, and missing alt text is on the list.