What should image alt text say?

Describe what the image conveys in context, in a sentence or so. If it is purely decorative, use an empty alt attribute — alt="" — which tells assistive technology to skip it. Both are correct; a missing attribute is not, because it leaves the technology to guess, and some will read the filename aloud.

Do images affect page speed rankings?

Substantially. Images are typically the largest resources on a page and the most common cause of a poor Largest Contentful Paint. Correctly sizing and compressing them is usually the single largest performance gain available on a real site.

SEO27 July 20266 min read

Free image SEO checker: the largest thing on your page, least examined

Images are usually most of a page's weight and most of its accessibility failures. Five changes fix ranking, load time and screen reader usability at once.

By Sapun Lamichhane · Arcetis

Images account for most of a typical page's transferred weight and a large share of its accessibility failures, and they receive less scrutiny than almost anything else because they are the part that looks finished.

Alt text, properly

Alt text describes what the image conveys, in context. The same photograph on a product page and in a blog post warrants different alt text, because it is doing a different job.

The distinction people miss is between empty and missing. alt="" is a decision — it tells assistive technology this image carries no information and should be skipped, which is exactly right for decoration. A missing attribute is an omission, and some screen readers respond by reading the filename aloud.

Dimensions, and layout shift

Explicit width and height let the browser reserve space before the image arrives. Without them the page reflows as each one loads, which is both visually unpleasant and a direct hit to Cumulative Layout Shift.

Serving the right file

Use modern formats — WebP or AVIF — with a fallback where you still need one.
Size the file to its displayed dimensions. A 4000px original scaled down in CSS costs the visitor the full download and gains nothing.
Compress. Most images on the web are two to five times larger than they need to be at indistinguishable quality.

Lazy loading, and the one exception that matters

Lazy-load images below the fold. Never lazy-load the largest image above it — that image is almost certainly your Largest Contentful Paint element, and deferring it delays the exact measurement you are being judged on. It is one of the most common self-inflicted performance problems there is.

What free means here

Our image SEO checker is free, with no account needed for your first scan. It reports missing alt attributes, missing dimensions, oversized files and images being scaled in the browser — and it distinguishes an empty alt from an absent one, because they mean different things.