Good image SEO comes down to four habits: upload photos at the size they are displayed, use modern formats such as WebP or AVIF, lazy load images below the fold, and give every meaningful image a short descriptive file name and honest alt text. Together they make pages faster and easier for Google to understand.
Key takeaways
- Google says alt text is the most important attribute for giving an image context, and it warns against keyword stuffing.
- Google Search supports BMP, GIF, JPEG, PNG, WebP, SVG and AVIF, so you are not stuck with JPEG.
- Lazy load images below the fold, but never your main hero image, which is often the largest element on the page.
- Oversized photos are a common cause of slow small business pages, and one of the easier things to fix.
- Descriptive file names and a sensible page layout help, but they are small signals. Do not expect an image tweak alone to change your rankings.
How big should my website images be?
Match the file to the space it fills. A photo displayed 800 pixels wide does not need to be uploaded at 4,000 pixels wide. A phone camera image can be several megabytes, and a visitor on a mobile connection pays for every byte.
The web.dev guidance on responsive images explains the idea behind srcset and sizes: you give the browser several widths of the same image and tell it how large the image will appear, and the browser picks the most efficient one for that visitor's screen. Most modern site builders, including Shopify themes, do this for you when you use the platform's image tools, so your job is mostly to upload a sensible original rather than a raw camera file.
As a rough working rule of our own, not a Google requirement: resize photos so the longest side is not much larger than the biggest size they will display (and a bit larger if you want sharpness on high-density screens), then compress. Check the result by eye. If you cannot see a difference, you compressed enough.
Always include width and height attributes on images. web.dev recommends them on every image tag because they let the browser reserve space before the image loads, which prevents the page from jumping around, known as layout shift. Most good themes already do this.
Which image format should I use: JPEG, PNG, WebP or AVIF?
Use the table to choose. The best format depends on the kind of image, and your platform may convert for you.
| Format | Best for | Notes |
|---|---|---|
| JPEG | Photographs, as a safe fallback | Works everywhere. Larger files than newer formats at similar quality. |
| PNG | Screenshots, graphics with sharp edges or transparency | Can be very large for photos. Avoid it for photographs. |
| WebP | Photos and graphics, as the everyday modern choice | Excellent support in modern browsers and generally smaller than JPEG. |
| AVIF | Photos where you want the smallest files | web.dev reports strong compression gains over JPEG and WebP; browser support arrived in Chrome and Opera in 2020, Firefox in 2021 and Safari in 2022. Keep a fallback for older browsers. |
| SVG | Logos, icons and simple illustrations | Vector, so it stays sharp at any size and is often tiny. |
If you are on Shopify, check what your platform already does. Shopify says that when a customer's browser supports modern formats such as WebP and AVIF, your images are delivered in those formats, and it also converts uploaded GIFs to animated WebP. In that case you do not need to convert files yourself. You still need to upload sensibly sized images and write good alt text, because no platform can write those for you.
When should I lazy load images, and when should I not?
Lazy loading tells the browser to wait on images that are off screen until the visitor scrolls near them. It saves bandwidth and speeds up the first view, and it is built into modern browsers with the loading="lazy" attribute.
The key rule from web.dev: do not lazy load images likely to be visible when the page first loads, especially your largest one. That main image, often the hero photo at the top of the page, is usually what the Largest Contentful Paint metric measures. web.dev says never to lazy-load it, because doing so delays the most important thing on the page. web.dev also suggests that a good Largest Contentful Paint is 2.5 seconds or less for at least 75 percent of visits. For a fuller look at speed targets, read our guide on how fast a website should load.
In practice: hero image loads normally, everything further down the page lazy loads.
What makes good alt text and file names?
Google says alt text is the most important attribute for giving an image context, and its example of good alt text is a plain description like "Dalmatian puppy playing fetch" rather than a stuffed phrase. The same advice covers real businesses: describe what is in the image, in the way you would tell someone on the phone, and include a place or service only when it is true and natural.
| Situation | Weak alt text | Better alt text |
|---|---|---|
| Photo of a finished kitchen remodel | kitchen remodel Fort Myers best contractor cheap kitchen | White shaker cabinets and a quartz island in a finished kitchen remodel |
| Team photo | team | Three technicians in uniform standing beside a service van |
| Logo that links to the homepage | logo | Company name, home page |
| Decorative divider or background flourish | blue swirl divider image | Leave the alt empty so screen readers skip it |
| Chart or screenshot | chart | Bar chart showing monthly phone calls rising from March to June |
File names work the same way. Google recommends short, descriptive file names such as my-new-black-kitten.jpg instead of IMG00023.JPG. Rename before you upload: white-shaker-kitchen-remodel.jpg tells Google and humans something that IMG_4471.jpg does not.
What is an image sitemap, and do I need one?
Google says an image sitemap lets you give it the addresses of images it might not otherwise discover, and that it can include images hosted on other domains, such as a content delivery network. If your images are ordinary img elements in your pages, Google can usually find them. In our experience, most small sites with a standard layout do not need a separate image sitemap. It becomes useful when images are loaded in unusual ways, for example from scripts or galleries.
One technical point from Google is worth knowing: Google does not index CSS background images as content. If an image matters for search, such as a product or a finished project, put it in the page as a normal image with alt text rather than as a CSS background. Also use the picture element or srcset for responsive versions, and keep a normal src as the fallback.
How do I audit my site's images in an afternoon?
- List your heaviest pages. Run a page speed test on your homepage and two top service pages and note the largest images.
- Find oversized files. Compare each image's file size to how big it appears on screen.
- Resize and compress. Export at the display size, use WebP or high-quality JPEG, and keep every file as small as looks good.
- Check the hero image. Make sure it loads normally and is not lazy loaded.
- Lazy load the rest. Confirm below-the-fold images use lazy loading and have width and height set.
- Rewrite alt text. Describe every meaningful image; leave decorative ones empty.
-
Rename generic files and replace anything uploaded as
IMG_1234where you can. - Retest. Run the same speed test and compare.
Do not save important text, such as a price list, only as a picture. Put it on the page as real text.
Where can I get help?
Image work is one part of on-page SEO, which our local SEO checklist for Fort Myers covers more broadly. Our On-Page SEO Setup at $299 includes writing image alt text for every image and a speed pass covering image sizing, compression and lazy loading, and our Standard SEO Optimization at $240 covers the technical baseline. We make no promises about rankings, because nobody can. If you are building from scratch, the Basic Website starts at $450.
Frequently asked questions
Do images really affect SEO?
Yes, in two ways. Image file size and loading behavior affect how fast your pages feel, which matters to visitors. Alt text, file names and surrounding text also help Google understand what an image shows, which can make it eligible to appear in image search. Images are one of many signals, though, and optimizing them will not by itself change your rankings. Treat it as part of good housekeeping.
Is WebP or AVIF better than JPEG for SEO?
Neither format is a ranking factor on its own. The benefit is smaller files at similar visual quality, which helps pages load faster. Google Search supports WebP and AVIF, and most modern browsers do too, though AVIF reached Safari later than Chrome and Firefox. Keep a JPEG or PNG fallback if your setup requires it. If your platform converts images automatically, as Shopify does for supported browsers, you may not need to do anything.
How long should alt text be?
Keep it short and specific, usually a phrase or one short sentence that describes what the image shows or what it does. Google advises being descriptive without keyword stuffing, and accessibility guidance says to convey the meaning the image adds. A cluster of keywords reads badly in a screen reader and can look spammy. If an image is purely decorative, leave the alt attribute empty so assistive technology skips it.
Should I lazy load every image on my site?
No. Lazy load images that are off screen when the page first opens, but do not lazy load your main hero image or any other image likely to be visible immediately. web.dev says lazy loading the largest image delays the part of the page visitors care about most and can hurt Largest Contentful Paint. A simple rule is to load the first screen normally and lazy load everything below it.
Do I need an image sitemap?
Usually not for a small site with standard images. Google describes image sitemaps as a way to point it to images it might not otherwise discover, so they help most when images are loaded through scripts or are hosted somewhere unusual. If your images appear as normal image elements in your page HTML, Google can typically find them. Check your own pages in Google Search Console before adding complexity.
Does my file name matter if I have alt text?
It matters a little. Google says descriptive file names give it clues about the subject of an image, and they cost nothing to write. Alt text does more of the work, so do not spend hours renaming old files. Name new uploads sensibly from now on, for example white-shaker-kitchen-remodel.jpg instead of IMG_4471.jpg, and fix the images on your most important pages first.
Sources
- Google Search Central: Image SEO best practices
- web.dev: Browser-level image lazy loading
- Shopify Help Center: Image guidelines
If you want a person to handle this on an existing site, see SEO and AI search in Fort Myers or ask about the services above. A human reviews every page we touch.
