Guide · Search
Image SEO: Alt Text and File Names That Help Search
Image SEO is the work of helping search engines and readers understand your pictures, and it comes down to a few habits: write plain alt text, name files clearly, and keep images sharp and light. This checklist follows Google and W3C guidance that was public by July 2022.
Start with the picture's job
Image SEO means making your pictures easy for people and search engines to understand. Google says images should add original value to a page, and that they work best near the text they relate to. So ask first: what does this picture do for the reader?
If a picture helps explain the page, keep it and place it close to the words that match. If it adds nothing, drop it. Google also advises against pages where neither the images nor the text are original.
Do not put important text inside an image. Page headings and menu items drawn as pictures cannot be read by everyone, and translation tools cannot reach them. Keep that text in HTML.
Sources: Google Search Central, Google Images best practices
Write alt text that describes
Alt text is a short description of an image. It helps people who use screen readers or have slow connections. Google also uses it, together with computer vision and the page content, to work out what an image shows.
Google gives a clear ladder. No alt text is bad. A stuffed list of keywords is bad too, and it can make a site look like spam. A single word such as "puppy" is better. A short, real description such as "Dalmatian puppy playing fetch" is best.
The W3C gives a simple guide for choosing:
- If the picture adds meaning, describe it briefly.
- If it is a link or button, say where the link goes or what the button does.
- If it is pure decoration, or repeats nearby text, use an empty alt attribute (alt="").
- If it is a chart or complex graphic, put the key information in the page text as well.
Alt text is also the anchor text when an image is a link, so write it with care.
Sources: Google Search Central, Google Images best practices; W3C WAI, An alt Decision Tree
Name files and folders in plain words
Google reads the file name and the URL path to learn what an image is about. Its own example is that my-new-black-kitten.jpg is better than IMG00023.JPG.
Use a short name that says what the picture shows. Put words in lowercase and join them with hyphens. Keep folders tidy, so image URLs follow a logical pattern. If you make a page in another language, Google says to translate the file names too.
Captions and nearby text matter as well. Google pulls clues about the subject from captions, image titles and the page around the picture.
Sources: Google Search Central, Google Images best practices
Keep pictures sharp and fast
Google notes that images are often the largest part of a page, which can make it slow and costly to load. Fast pages are better for readers, and Google points site owners to PageSpeed Insights to test them.
Quality counts too. Google says clear, sharp photos appeal to people more than blurry ones, and they look better in small result thumbnails. Pick one of the formats Google Images supports: BMP, GIF, JPEG, PNG, WebP or SVG.
For different screen sizes, use the srcset attribute or the picture element. Always keep a normal img tag with a src value as a fallback, because some browsers and crawlers do not understand the newer markup.
Many people search on phones. Google says more people use Google Images on mobile than on desktop, so test that your pages work on small screens.
Sources: Google Search Central, Google Images best practices
Help Google find every image
Google reads the HTML of your pages to find images. It does not index CSS background images. So use a real img element for any picture you want found, not a div with a background-image style.
If some images are hard to discover, you can submit an image sitemap. Unlike a normal sitemap, it may list image URLs hosted on other domains, such as a content delivery network.
You can also add structured data. For Product, Video and Recipe pages, Google says the image property is needed to qualify for a badge and rich result in Google Images. Check the page title and description too, since Google uses them to build the title link and snippet.
Sources: Google Search Central, Google Images best practices
A quick image SEO checklist
Check Pass if Purpose The picture helps the reader and sits near related text Alt text A short, true description, with no keyword lists Decorative images They use an empty alt attribute File name Words joined by hyphens that say what the picture shows Format and size A supported format, sharp, and not larger than needed Markup An img element with a src, not a CSS background Text in images Headings and menus stay as real HTML text Run the table over your ten most visited pages first. Fix the missing alt text and the file names that look like IMG00023, then look at page weight.
Sources: Google Search Central, Google Images best practices; W3C, Understanding Success Criterion 1.1.1: Non-text Content; W3C WAI, An alt Decision Tree
Sources