Imagine planning a kitchen-appliance page with a photo of its control panel. A buyer could use it to see where the settings are. A generic kitchen photo may look attractive, but it cannot answer that question.
Image SEO means choosing images that help the page, describing their meaning for people who cannot see them, and making the files understandable and accessible to search engines. The work starts with the reader's question, not with a filename or a list of keywords.
What Does Image SEO Do?
An image can show a product feature, explain a process, or make a comparison that words alone would make harder. Google uses the image, its alt text, and the surrounding page to understand its subject. A good image does not replace a useful page; it works with the page's title and explanation.
On an appliance page, a control-panel photo can show the layout while nearby text explains what each setting does. A separate dimensions diagram needs labeled measurements. Neither image should carry information the page never explains in text.
Which Image Belongs on the Page?
Ask what a visitor needs to see before deciding. For the appliance page, that might be the controls, dimensions, or installation clearance. A decorative image can support the design, but should not be presented as evidence of a feature or result.
Put an informative image near the paragraph it helps explain. Add a short caption when readers need to know what to notice. Reusing the same generic image across unrelated guides hides what is specific about each page.
How Do You Write Useful Alt Text?
Alt text gives a text alternative when an image cannot be seen. Write it for the image's job on this page, not for a target keyword. A product photo might use “Black induction hob with four cooking zones and front touch controls” if those details are visible and relevant.
- Informative image: briefly describe the information it adds.
- Image-only link: describe the destination or action, such as “View installation dimensions.”
- Decorative image: use an empty
alt=""so a screen reader can skip it. - Complex chart: give a short label and explain the important data in nearby text.
Include an alt attribute on the image; alt="" deliberately marks decoration, while omitting the attribute can leave its purpose unclear. Do not fill alt text with repeated search terms or rely on a file name when a specific description would help. If nearby visible text already gives the full meaning and the image adds nothing, an empty alt may be appropriate.
How Do Search Engines Find and Understand an Image?
Use a normal HTML <img> with a working src for an important content image. Google can find images in that attribute, including an <img> inside <picture>; it says it does not index CSS background images. A background is fine for decoration, not for a diagram or product detail that the page depends on.
The page's text and any caption give the file context. A short descriptive filename is a small clue, not a substitute for a relevant image. If a content image only appears after interaction or its file URL is blocked, check the rendered page and whether the file can be fetched.
Which File and Size Should You Publish?
Choose a format by the image's job and the output you can inspect. JPEG, WebP, and AVIF can work well for photos. PNG is a simple lossless choice for some graphics, while WebP can also be lossless or transparent. Compare file size and visible detail rather than assuming one format always wins.
Export enough pixels for the display size without sending the original large file to every phone. Responsive images can offer smaller and larger versions through srcset, with a working src fallback. Set dimensions or an aspect ratio so the page can reserve space before loading. The Core Web Vitals guide covers loading priority and layout shifts in more detail.
How Do You Check One Page?
- For each image, name the reader question it helps answer. If there is none, treat it as decoration or remove it.
- Check alt text by job: information, link action, decoration, or complex data.
- Confirm the image file loads in an
<img src>and sits near relevant text. - Compare desktop and mobile. Can readers see the useful detail without downloading a needlessly large file?
Fix the image that blocks understanding before changing filenames across the whole library.
Frequently Asked Questions
Does Alt Text Help Image SEO?
Yes. Google uses alt text with the image and page context to understand its subject, and it gives people who cannot see the image an alternative. It does not rescue an irrelevant image or an unhelpful page.
How Do You Write Good Alt Text?
Describe the image's useful meaning or action in its page context, briefly and naturally. Use alt="" for images that are purely decorative or fully redundant.
Is PNG or WebP Better?
Neither is always better. Compare file size and visible quality for the actual image. WebP often compresses well and can be lossless or transparent; PNG is another lossless choice for graphics.
What Is the Best Image Size for SEO?
There is no universal pixel or kilobyte target. Match the image to its displayed size and keep important details clear, especially on a phone.