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Image SEO Checker: alt text, file names, formats and sizes

Check alt text, file names, formats, width and height, lazy loading and file sizes on any page.

  • Free to use
  • Nothing to install
  • No sign-up

How to use the Image SEO Checker

Read what the guide says

This is the Image SEO Checker.

It checks every image on a page: alt text, file names, formats, sizes and loading.

Use it on pages with photos: Google uses alt text and file names to understand an image.

It also checks width and height, which stop the page jumping while images load.

Enter the address of a page with images.

Or press Try an example: a sample gallery page of a made-up dental clinic.

Press Check images. We read the page once, and ask each image file for its size.

You get a score out of a hundred, from our checklist, not a Google measure.

The tiles count the images, any without alt text or width and height, and their total size.

This box lists what to fix first: a photo with no alt text, and a TIFF file Google does not index.

Open How to fix to see why it matters and the steps.

Here, give the photo alt text that says what it shows, in a few words.

Choose the platform your site runs on to see where to add alt text.

Every image is listed in page order, with its alt text and what to fix.

Here, one alt text says only "image", and another repeats "dentist" three times.

Download the CSV, to share it with whoever looks after your site.

Fix the images, then check the page again.

You can also email yourself a PDF of the result.

Any page with images. We read the page as it is sent, without running scripts, and ask each image for its file size.

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About the Image SEO Checker

Enter a page address. We read every image in the page's HTML and check what Google's image guidelines and web.dev ask for: alt text that describes the image, file names that say what it shows, formats Google Search indexes, width and height so the page does not jump while loading, no lazy loading on the first image, real image addresses in the HTML, and file sizes. You get a table of every image with its problems, and how to fix them.

How it works

  1. Step 1

    Enter the address of a page with images.

  2. Step 2

    We read the page once and ask each image file for its size, without downloading it.

  3. Step 3

    Fix what is flagged: rewrite alt text, rename files before you upload them, add width and height, and compress heavy images.

What Google looks at

Google finds images in the src of <img> elements, including those inside <picture>, and does not index images set in CSS. It uses alt text, the file name and the text around an image to understand it, and indexes BMP, GIF, JPEG, PNG, WebP, SVG and AVIF files. Google warns against filling alt text with keywords.

Speed and layout

web.dev advises setting width and height on images so space is kept while they load, which stops the page jumping, and loading images that are visible when the page opens straight away rather than lazily. Google publishes no file size limit for images; the 200 KB in this tool is our measure for a photo on a web page.

What this tool cannot do

It reads the page as it is sent, without running scripts, so images added by JavaScript are missed. It cannot see what is in an image, so it cannot tell whether alt text is accurate, only whether it looks like a description. File sizes come from the server's headers, for up to 20 images.

Frequently asked questions

What is good alt text?

A few words that say what the image shows, as you would describe it to someone who cannot see it: "Dr Meera explaining a dental X-ray to a patient" rather than "dentist image". Use a keyword only where it really describes the image. Decorative images such as icons and dividers should have empty alt text (alt="") so screen readers skip them.

Do image file names matter for SEO?

Google says the file name can give it clues about what an image shows: teeth-whitening-before-after.jpg says more than IMG00023.JPG. Rename files before you upload them, with a few words joined by hyphens. For images already live, rename them when you next replace them, and update every page that uses them.

Which image format is best for websites?

Google Search indexes BMP, GIF, JPEG, PNG, WebP, SVG and AVIF. For photos, WebP and AVIF files are usually smaller than JPEG at similar quality; PNG suits graphics with sharp edges, and SVG suits logos and icons. Avoid HEIC (iPhone photos) and TIFF, which Google Search does not index and many browsers cannot show.

Should I lazy-load images?

Lazy-load images further down the page with the browser's own loading="lazy" attribute, which needs no script. Do not lazy-load images that are visible as soon as the page opens, such as the main image at the top: web.dev advises loading those straight away. If a script lazy-loads images, Google asks that it loads them as they come into view, without waiting for a scroll.

How big should images be?

Google publishes no file size limit, but large files slow pages down, especially on mobile data. Resize each image to the largest size it is shown at, compress it, and offer smaller versions to phones with srcset. This tool flags files over 200 KB, which is our measure, not a Google rule.

Related reading

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