Images are easy to forget in an audit. Pages get checked for titles, links and status codes, while a template quietly outputs hundreds of product photos with no alt text, or a CDN change leaves the blog full of broken images.
This guide covers the two image problems worth checking on every site, how to write alt text that actually helps, and how to find both problems across every page.
Why does alt text matter?
Alt text does three jobs:
- Accessibility. Screen readers read it aloud. Without it, people using them miss what the image shows.
- Fallback. Browsers show it when the image doesn’t load.
- Search. Google’s image SEO best practices call alt text “the most important attribute when it comes to providing more metadata for an image”, and say Google uses it “along with computer vision algorithms and the contents of the page to understand the subject matter of the image.”
What makes good alt text?
Google asks for alt text that is “useful, information-rich content that uses keywords appropriately and is in context of the content of the page”, and warns that keyword stuffing creates a negative experience and may cause a site to be seen as spam.
| Image | Weak alt | Better alt |
|---|---|---|
| Product photo | shoe |
Trail Runner 2 in red, side view |
| Chart in an article | chart |
Organic clicks doubled after the redirect cleanup in March |
| Team photo | team team photo best seo team |
The support team at the Hanoi office |
| Divider or background flourish | decorative line |
alt="" (decorative) |
Decorative images get an empty attribute, alt="". W3C’s guidance on decorative images explains why: it lets screen readers ignore them. Leaving the attribute out is not the same thing, because some screen readers then read out the file name instead.
Two more points from Google’s guidance: use standard <img> elements (Google finds images in the src attribute and doesn’t index CSS background images), and use descriptive file names, which give “very light clues” about the subject.
Why do images break?
- Files deleted or renamed in the media library
- CDN or domain changes that didn’t update stored URLs
http://image URLs after an HTTPS move (see HTTPS and mixed content)- Hotlinked images from sites that removed them
A broken image looks neglected to visitors and wastes requests for crawlers.
How do you find image problems across a site?
Checking a page in the browser shows you that page. To cover every page, crawl the site and check every <img>. Crawlens records each image on every crawled page, with its alt attribute, and runs two checks:
| Check | What it flags | Severity |
|---|---|---|
| Images missing alt text | Pages with images that have no alt attribute at all, with the list of images | Warning |
| Broken images | Pages with internal images that fail to load | Warning |
Images with alt="" aren’t flagged as missing, so decorative images marked correctly don’t create noise. The broken image check needs Check images turned on for the crawl; it’s on by default and requests every internal image after the crawl.
How do you fix them at scale?
- Group by template. Missing alt text usually comes from one component: the product gallery, the blog card, the logo strip. Fix the component so it always outputs alt text from a sensible field (product name and variant, image caption, article title).
- Make alt text a required field in the CMS for content images, with an explicit “decorative” option that outputs
alt="". - Fix broken images at the source. Restore the file, update the URL in the template or content, or remove the image.
- Re-crawl and compare. Both checks should show the affected pages as fixed.
Checklist
- Every meaningful image has descriptive alt text in context
- Decorative images use
alt="", never a missing attribute - No keyword stuffing in alt text
- Important images use
<img>, not CSS backgrounds - Descriptive file names for new uploads
- No broken internal images
- Image URLs updated after CDN, domain or HTTPS changes
Frequently asked questions
What is alt text?
Alt text is the text in an image's alt attribute that describes it. Screen readers read it aloud, browsers show it when the image fails to load, and Google uses it to understand what the image shows.
Does alt text help SEO?
Yes. Google says alt text is the most important attribute for providing image metadata, and uses it along with computer vision and the page content to understand an image, which helps images appear in Google Images.
What alt text should decorative images have?
An empty alt attribute, alt="". W3C recommends it so screen readers skip the image. Leaving the attribute out entirely is different, because some screen readers then read out the file name.
How long should alt text be?
Long enough to describe what matters about the image in context, usually a short phrase or sentence. Don't stuff keywords; Google warns it creates a bad experience and may be seen as spam.
Does Google index CSS background images?
No. Google finds images in the src attribute of img elements and doesn't index images set in CSS. Use a standard img element for images you want found.