Free on-page seo check

Image SEO and Alt Text Checker

Images without alt text are invisible to screen readers and image search. Oversized and legacy images slow the page down. Check both in one go.

Check images

Enter a page. Its images are listed with their alt text and formats.

Checks in this tool:page.image-alt perf.image-formats

Why use the Image SEO Checker

Missing alt text

Every image without an alt attribute is listed by its source, so you know exactly which ones to fix.

Decorative images respected

An empty alt attribute marks an image as decorative and is not reported.

Modern formats

JPEG, PNG and GIF images that could be served as WebP or AVIF are listed.

Oversized images

When a browser is available, images much larger than their display size are flagged.

When to use the Image SEO Checker

Accessibility fixes

Get the list of images that screen readers cannot describe.

Image search

Alt text is how search engines understand images.

Speed work

Find the heavy images worth converting first.

E-commerce

Product photos need descriptive alt text and modern formats.

CMS uploads

Editors forget alt text. Check new articles before publishing.

Theme audits

Logos and icons in templates often lack alt text on every page.

Understanding Image SEO

Writing alt text

1Describe the purpose. Say what the image shows or does in context, in a short sentence.
2Links and buttons. For an image inside a link, describe the destination.
3Decorative images. Use alt="" so assistive technology skips them.
4No stuffing. Keywords that do not describe the image help nobody.

Modern image formats

WebP is supported by every current browser and is usually 25 to 35 percent smaller than JPEG at the same quality. AVIF is smaller still. Serve them with a picture element and a fallback, or let an image CDN negotiate the format.

Size matters more than format

A 4000 pixel photo shown at 400 pixels wastes far more than any format change saves. Serve images at the size they are displayed, with srcset for different screens.

Privacy, safety and limits

The page is fetched by AbackAuditBot from Aback servers with an ordinary GET request. No cookie, password or form data is sent, and nothing on the site is changed.

The tags are read from the HTML the server sends. Tags that a script adds after the page loads are not seen, and neither are they by most crawlers and preview bots.

Related tools and guides

Page Speed TestMeasure how fast a page answers and renders on a throttled mobile profile, and find the causes: heavy pages, missing compression, uncached assets and render blocking scripts.Accessibility CheckerFind the accessibility problems that automated testing can catch reliably: missing labels, unnamed buttons, broken ARIA, missing landmarks and text that is hard to read.Open Graph CheckerWhen someone shares your page, the preview comes from its Open Graph and Twitter card tags. Check that they are complete and see a preview of the card.Heading CheckerHeadings are the outline of a page for screen readers, search engines and AI assistants. See the outline of any page and fix skipped levels, empty headings and missing or duplicate H1s.SEO CheckerFind the technical problems that keep a page out of search results. The checker reads the page the way a search crawler does and lists what to fix first, with the evidence behind every verdict.Meta Tag CheckerSee the title and description a search engine reads, how the result could look, and whether the canonical, robots, viewport and language tags are set correctly.

Frequently asked questions

Does every image need alt text?

Every image needs an alt attribute. Images that carry meaning need a description, decorative images need an empty alt="".

How long should alt text be?

Usually one short sentence. Screen readers read all of it, so keep it to what the image adds.

Does alt text help SEO?

It helps image search and gives context to the page. Its main purpose is accessibility.

Should I use WebP or AVIF?

WebP for broad support today, AVIF where you can provide a fallback. An image CDN can choose per browser.

Are CSS background images checked?

No. Background images are decoration and carry no alt text. Do not put meaningful images in CSS backgrounds.

Why are SVG images not reported as legacy?

SVG is already a modern, scalable format for icons and illustrations.

How are oversized images measured?

With a headless browser that compares each image's natural size with its displayed size. Without a browser that part is skipped and the report says so.