Image SEO & alt text
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
Google cannot see images the way humans can. It relies on alt text — a written description — to understand what each 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: Google uses it to understand what an image depicts, since it can't "see" images the way humans can.
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"
- Under about 125 characters
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. It doesn't describe the image, and Google recognizes it as keyword stuffing.
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 reads file names as part of understanding images.
Bad: IMG_4729.jpg
Good: handmade-ceramic-mugs-blue.jpg
Use lowercase letters, separate words with hyphens, and keep it short but descriptive.
Image file size and SEO
Large image files slow your page down. Page speed is a ranking factor, 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. If you'd like help, just ask.
Where to add alt text
When you upload an image in the Media Library or insert it in a page, look for the "Alt Text" field in the attachment details panel on the right. Fill it in before inserting the image. You can also edit alt text on any existing image by opening the Media Library and clicking the image.
When you add or select an image in the Designer, look for the "Alt text" field in the right-hand settings panel. You can also add alt text through the CMS for images stored there.
Click on any image block to select it, then look for the caption/accessibility settings. Squarespace has a dedicated alt text field in the image settings panel.
Common questions
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