Image SEO and Alt Text: The Optimization Most Businesses Skip
Written by Gabriel Bertolo
July 6, 2026
Images are an entity signal, not decoration. And because most businesses ignore image SEO entirely, doing it well is one of the easier edges you can get in search.
Think about how much effort goes into the words on a page and how little goes into the images. People agonize over their copy, then upload a photo straight off their phone named IMG_4521.jpg with no alt text, no compression, and no thought about what it signals. That gap is the opportunity. The businesses that treat images as a genuine optimization channel pull in traffic and signals that their competitors never bother to claim.
Honestly, this is the part of an audit where I get a little excited, because the wins are so easy and so overlooked. I’ll be reviewing a beautiful site for a Northampton retailer or a Pioneer Valley restaurant, the kind of business that lives and dies on how its products look, and find that every single mouthwatering photo is a giant uncompressed file with a filename like DSC_0094.jpg and an empty alt attribute. All that gorgeous visual content, completely invisible to search engines and dragging the page speed down on top of it. It’s frustrating to see, but it’s also the good kind of problem, the kind you can fix in an afternoon and watch pay off.
Image SEO is really two jobs in one. Making your images discoverable, so they pull traffic from image search and visual tools. And making sure they don’t slow your site down, because heavy images quietly wreck your page speed. Skip either half, and you forfeit the results you’ve already done most of the work to earn. And the stakes are bigger than people assume.
Google Images drives 22.6% of all web traffic. Source: Digital Applied.
This guide is part of our complete guide to on-page SEO, and it covers how to make your images work as hard as your words.
Image SEO sits at the intersection of two things that both matter for rankings: discoverability and performance.
On the discoverability side, images are their own search channel. People search Google Images directly. And visual search has become a genuine commercial channel.
Google Lens now processes over 12 billion visual queries per month. Source: Digital Applied.
For product-based businesses, especially, optimized images capture shopping intent before a user even types a query. That’s a discovery path most sites completely ignore.
On the performance side, images are usually the heaviest things on a page. Unoptimized images are the single most common reason a page loads slowly, and slow pages hurt both rankings and conversions. So image optimization isn’t just about image search. It directly affects your Core Web Vitals and your overall page experience.
And there’s a newer dimension. Modern AI systems analyze images directly now. They’re multimodal, meaning they process visual content alongside text. The context you provide through alt text, filenames, and surrounding content feeds how these systems understand your page. Images have gone from being invisible to search engines to being a signal that they actively read.
Alt text is the most important image SEO element, and it’s the one most teams get wrong.
Alt text, the alt attribute, is a description of an image written into the HTML. It serves two audiences that happen to want the same thing. Screen reader users rely on it to understand visual content they can’t see, which makes it an accessibility requirement under standards like WCAG 2.2. And search engines use it as the primary signal for understanding what an image shows. Both audiences are best served by the same thing: a clear, accurate description of what’s actually in the image.
Here’s how to write it well. Describe the image factually, starting with the subject. Keep it concise, generally in the 80 to 125 character range. Include your relevant keyword once, naturally, only where it genuinely fits the image. And skip openers like “image of” or “photo of,” because search engines already know it’s an image. Use that space to describe instead.
The most common mistake is treating alt text as a metadata field to stuff with keywords. Repeating your target keyword across every image’s alt text triggers over-optimization flags and helps nobody. Writing identical alt text for multiple images on the same page wastes the opportunity, because each image is a unique asset. And forgetting alt text entirely, which is rampant, leaves both accessibility and ranking value on the floor. Write each one to genuinely describe its image, and the SEO value follows.
Before a search engine even reads your alt text, it reads your filename. That’s your first opportunity to tell it what the image is.
IMG_4521.jpg tells a search engine nothing. A descriptive filename like blue-running-shoes-mens-size-10.webp tells it exactly what the image shows. The difference is the difference between a wasted signal and a useful one.
The rules are simple. Use real words that describe the image. Separate them with hyphens, not underscores or spaces. Keep it concise but specific. And do this before you upload, because renaming images after they’re live and linked across your site is a headache you don’t need. Descriptive filenames are one of the easiest wins in all of image SEO, and almost nobody does them.
The format you serve your images in is the single biggest lever for image weight, and serving old formats means shipping bytes you have no reason to ship.
WebP is the universal baseline now. It’s supported in every browser you should care about and delivers files that are 25 to 35% smaller than JPEG at equivalent quality. Source: Digital Applied. It also handles transparency, so it can replace PNG. If your content management system supports nothing else, WebP is the correct default.
AVIF is the upgrade. It delivers files up to 50% smaller than JPEG, which is a substantial speed gain. The tradeoffs are that AVIF encoding is more CPU-intensive, and support gaps remain on some older browsers. The clean way to handle this is to serve AVIF first through the HTML picture element, fall back to WebP, and use JPEG or PNG only as a final fallback for legacy browsers. That way, every visitor gets the best format their browser supports, with no visible difference in quality.
For icons and simple graphics, SVG is the right choice, since it scales infinitely at tiny file sizes. The summary: WebP as your default, AVIF as the upgrade with fallbacks, SVG for icons, and JPEG or PNG only as a safety net.
Format is the biggest lever, but compression and sizing matter just as much for performance.
Compress your images before serving them. Good compression tools cut file size dramatically with no visible quality loss. There’s rarely a reason to serve a full-resolution image straight from a camera or design tool.
Size images appropriately, and use responsive images to serve the right size for each device. A mobile visitor on a product page does not need to download a 2,400-pixel-wide image meant for a desktop display. The srcset attribute lets you serve different image sizes based on the visitor’s screen, so phones get smaller files and large screens get larger ones. Serving appropriately sized images reduces data transfer and directly improves your Core Web Vitals.
This is where image SEO connects to your broader technical performance. Heavy, oversized images are one of the most common causes of poor Largest Contentful Paint scores, which we cover in our guides to mobile-first web design and the full technical SEO audit.
Lazy loading defers the loading of off-screen images until the user scrolls near them. It’s a genuine performance win, because the browser doesn’t waste time loading images nobody has scrolled to yet.
But there’s one critical exception, and getting it wrong does real damage. Never lazy-load your LCP image, the largest, most prominent image in the initial view, usually your hero image. Lazy-loading the hero image delays the very thing that determines your Largest Contentful Paint score, which tanks that Core Web Vital. Instead, preload the hero image and mark it with high fetch priority so the browser loads it as fast as possible. Lazy-load everything below the fold, and prioritize the image at the top.
This single distinction trips up a lot of well-intentioned sites. They enable lazy loading globally, including on the hero image, and wonder why their LCP got worse instead of better.
Here’s the framing that elevates image SEO from a technical checklist to a strategic signal. Your images are evidence of what your entity is.
Because modern AI systems analyze images directly, the visual content on your page either reinforces or undermines what your page claims to be about. An article about a specific service that shows real photos of that service being performed reinforces the entity. A page full of generic stock photos of people in suits shaking hands reinforces nothing.
This matters especially for local and service businesses. Original photos of your actual team, your actual location, and your actual work verify that you’re a real entity doing real things in a real place. Stock photography can’t do that. When a search engine or AI system reads your images alongside your text and they tell the same story, that coherence strengthens how confidently the system understands your business. Image-text coherence is a trust signal, and original imagery is how you earn it. This connects directly to the entity work we do in our generative engine optimization services.
Two more steps help search engines find and understand your images.
An image sitemap, or image entries within your existing sitemap, helps search engines discover images they might otherwise miss, especially images loaded through JavaScript or CSS. For image-heavy sites, this is worth setting up. Organizing your images logically in the file path, grouping them by topic rather than by upload date, also helps search engines understand the context of an image from its path alone.
Structured data adds another layer. ImageObject schema and product image markup give search engines explicit, machine-readable information about your images, which can help them appear in rich results and visual search features. For e-commerce especially, complete image structured data improves the odds of showing up in shopping and visual search. We cover the broader structured data picture in our guide to schema markup.
What is alt text?
Alt text is a written description of an image, added in the HTML alt attribute. It helps screen reader users understand visual content and serves as the primary signal search engines use to understand what an image shows. It’s both an accessibility requirement and the highest-impact image SEO element.
How long should alt text be?
Generally 80 to 125 characters. Describe the image factually, start with the subject, include your relevant keyword once where it fits naturally, and skip openers like “image of” or “photo of.” Keep it concise but genuinely descriptive of what’s in the image.
What is the best image format for SEO?
WebP is the universal baseline in 2026, delivering files 25 to 35% smaller than JPEG. AVIF is the upgrade, up to 50% smaller, served with WebP and JPEG fallbacks through the picture element. Use SVG for icons and simple graphics. Serving plain JPEG or PNG leaves performance on the table.
Does image SEO help rankings?
Yes, in two ways. Optimized images pull traffic from Google Images and visual search, which drives a significant share of all web traffic. And properly compressed, correctly sized images improve your page speed and Core Web Vitals, which are ranking factors. Image SEO helps both discoverability and performance.
Should I lazy-load all images?
Lazy-load off-screen images, but never lazy-load your LCP image, usually the hero image at the top of the page. Lazy-loading the hero delays your Largest Contentful Paint and hurts that Core Web Vital. Preload the hero with high fetch priority instead, and lazy-load everything below the fold.
Image SEO is the optimization most businesses skip, which is exactly why doing it well gives you an edge. Descriptive alt text, modern formats, proper sizing, and smart loading turn your images from dead weight into a genuine source of traffic and signals.
For how image optimization fits with everything else on the page, read our complete guide to on-page SEO. And if you’d like us to audit how your images are helping or hurting your site, get in touch.
Gabriel Bertolo is a 3rd generation entrepreneur who founded Radiant Elephant over 13 years ago after working for various advertising and marketing agencies.
He is also an award-winning Jazz/Funk drummer and composer, as well as a visual artist.
His Web Design, SEO, and Marketing insights have been quoted in Forbes, Business Insider, Hubspot, Entrepreneur, Shopify, MECLABS, and more.
Check out some publications he's been quoted in:
Quoted in HubSpot's AI Search Visibility Article and HubSpot's Article on 6 Best Wix Alternatives
Quoted in DesignRush Dental Marketing Guide
Quoted in MECLABS
Quoted in DataBox Website Optimization Article and DataBox Best SEO Blogs
Quoted in Seoptimer
Quoted in Shopify Blog