Image SEO & alt text
How images affect your search rankings: what Google reads from alt text, file names and file size, and how to show up in Google Images.
Images make your website more engaging. They also affect your SEO, both through how Google reads them and how they affect your page load speed.
This guide explains how to handle images for the best SEO results.
Alt text and Google
Alt text (short for alternative text) is a written description of an image. It was designed for people using screen readers, and it also serves an SEO purpose. In Google's words, it "uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image".
The same alt text serves both jobs, so write it for people first: a clear, specific, honest description of what the image shows, written as a phrase rather than a list of keywords. For how to write it, when to leave it empty for decorative images, and where to add it in WordPress, Webflow and Squarespace, see alt text explained.
What alt text is NOT for
Alt text should describe the image, not be a place to stuff keywords.
Avoid: alt="seo services denver seo company best seo agency"
That's spam. Google's own instruction is to "avoid filling alt attributes with keywords (also known as keyword stuffing) as it results in a negative user experience and may cause your site to be seen as spam".
A keyword can appear in alt text if it naturally belongs there. For example, if an image shows your product, the product name (which may be your keyword) belongs in the description.
Image file names
Before you upload an image, name the file descriptively. Google says "the filename can give Google very light clues about the subject matter of the image": light, but free.
Bad: IMG_4729.jpg
Good: handmade-ceramic-mugs-blue.jpg
Use lowercase letters, separate words with hyphens, and keep it short but descriptive. Google's advice is the same: use filenames that are short but descriptive, and avoid generic ones like image1.jpg.
Image file size and SEO
Large image files slow your page down. Speed is part of the page experience Google's ranking systems reward, and heavy images are one of the most common causes of slow sites.
Before uploading, resize and compress your images:
- Photographs: JPEG or WebP format, under 200KB where possible
- Graphics and logos with transparency: PNG or SVG
Most content management systems (WordPress, Webflow, Squarespace) can compress images automatically, or we can set this up with a plugin. Squarespace, for example, automatically makes smaller copies of each image for different screen sizes and, by default, shows them in the lighter WebP format, but it still recommends uploading images of 500 KB or less. If you'd like help, just ask.
Common questions
What if I have hundreds of images with no alt text?
Don't panic. Start with your most important pages: homepage, service pages, product pages. Work through the rest over time. We can audit your site for missing alt text if needed.
Does alt text help with Google Images?
Yes. Well-described images with clear alt text are more likely to appear in Google Images searches. This can be a meaningful source of traffic for some businesses, particularly those selling physical products or creative work.
What format should I use for images on my website?
WebP is the sensible default for photographs and most images now: MDN reports that lossy WebP files are on average 25 to 35% smaller than JPEG files of visually similar quality, and lossless WebP files about 26% smaller than the same image as a PNG. JPEG still works well for photographs. PNG is best for graphics with text or transparent backgrounds. SVG is ideal for logos and icons. Google Search supports all of these: BMP, GIF, JPEG, PNG, WebP, SVG and AVIF.
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