Image SEO: The Practical Guide Almost Nobody Applies

Open your website and look at the name of any image. If it says IMG_4032.jpg or final-photo-v2-FINAL.png, you're leaving traffic on the table. On almost every website, images are the heaviest files and the worst used: they slow the page down and tell Google nothing about what they show.

Image SEO pays out two different prizes. The first is speed: optimising images is the most profitable performance improvement there is. The second is visibility: Google Images is an enormous search engine where competition is minimal in most industries. This guide covers both, with rules you can apply today.

Why images matter more than you think

Google doesn't "see" an image the way a person does: it reads the signals around it — the file name, the alt text, the nearby copy, the caption. From those signals it decides whether your photo shows up in Google Images, in the image pack of a normal search, even in shopping results. For visual businesses — restaurants, real estate, workshops, stores — that's real traffic: someone searches "modern white fitted kitchen" and lands on your project.

And there's a second, less visible effect: images weigh more than the entire rest of the page combined. A homepage with ten uncompressed photos can weigh 8 MB; the same page with optimised images, under 1 MB. That difference is loading speed, and speed is a ranking factor we cover in depth in Core Web Vitals.

The file name and the alt text

These are the two most direct signals, and the two almost nobody writes. Concrete rules:

• Descriptive file names in kebab-case: white-fitted-kitchen-quito.jpg, not IMG_4032.jpg. It gets written before uploading; renaming afterwards rarely happens.
• Alt text that describes what's visible, in one natural sentence: "White fitted kitchen with a central island and black taps". Not empty, not "photo1", not a keyword list.
• Don't force the keyword into every alt: if you have twenty kitchen photos, describe them differently. The exact same phrase twenty times is spam to Google and noise to screen reader users.
• Decorative images (textures, flourishes): empty alt (alt="") so screen readers skip them. Decorating isn't informing.

Format and weight: the technical part in three decisions

On weight, an honest reference: a normal content photo shouldn't exceed 150–250 KB; a full-screen cover image, 400 KB. On a well-built website, WebP conversion and compression happen automatically at upload — it's one of the things separating a professional site from a template. If it's manual, free tools like Squoosh solve it in seconds.

Dimensions, lazy loading and the page jump

• Upload the image at the size it will be shown. A 4000-pixel photo in an 800-pixel column is wasted weight: the browser shrinks it, but downloads the whole thing.
• Lazy loading: images further down the page shouldn't load until the user approaches them. It's standard on modern sites; check yours does it.
• Reserve each image's space (declared width and height): it stops the text from "jumping" while photos load — that jump is an official Google metric (CLS) and a real annoyance for users.
• The hero image is the exception: the first visible image must load immediately and at high priority, never lazily.

Product images: where SEO turns into money

In an online store, images do double duty: they convince the buyer and they compete in Google Images and shopping results. The rules above apply with extra discipline — a name per product and variant, alt text including brand and model, a clean background for the main shot and usage context in the secondary ones. The full detail of how to build the page is in product pages that convert.

Your own photos or stock: the short answer

Google doesn't penalise stock, but it doesn't reward it either: a photo that appears on ten thousand websites carries no distinctive signal at all. Your own photos — your premises, your team, your actual work — are the only ones that can rank in local image searches and the only ones that build trust on arrival. The practical rule: stock for illustrating abstract concepts, your own photos for everything you sell. And all of this, remember, is one piece of your overall SEO strategy, not an isolated trick.