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How images affect your search rankings, what alt text is, and how to write it correctly for both SEO and accessibility.

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.

Quick summary

Alt text — a written description of an image — is what Google calls "the most important attribute when it comes to providing more metadata for an image". Google combines it with computer vision and the rest of the page to work out what an image shows. Write clear, descriptive alt text for every meaningful image. Also name your image files descriptively before uploading, and keep file sizes small to protect page speed.

What is alt text?

Alt text (short for alternative text) is a written description of an image. It was originally designed for visually impaired users who use screen readers — software that reads web pages aloud. The screen reader reads the alt text when it reaches an image.

Alt text 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".

Good alt text is:

A clear, honest description of what the image shows
Written as a sentence or phrase, not a list of keywords
Specific — "golden retriever puppy sitting on a green lawn" rather than "dog"
Short: think about how you'd describe the image to someone over the phone, in one breath

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.

Decorative images

Not every image needs alt text. Decorative images — purely visual elements that don't add meaning, like background patterns or dividers — should have an empty alt attribute (alt="").

This tells screen readers to skip the image, which gives a better experience for visually impaired users.

For photos that illustrate your content, always write meaningful alt text.

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.

Where to add alt text

Two places, and the difference matters. In the Media Library, the Alt Text field sets the default that gets used whenever you insert that image. On a page, select the Image block and fill in Alternative text in the block settings — that version applies only to this page or post. The same panel has a Mark as decorative option for images that carry no meaning.

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.

Should I describe exactly what I see, or why the image is there?

Describe what you see — the actual content of the image. "A woman reviewing documents at a desk" is better than "business productivity." The context of why it's on the page comes through in the surrounding content.

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 25–35% 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.

Need a hand?

If you're stuck, email support@chykalophia.com and we'll help. Include your website address and a screenshot if you can.

Image SEO & alt text