Image SEO: Alt Text, File Names & More

Your website’s images are working against you right now. I know that sounds harsh, but it’s probably true. Most people upload images without giving a second thought to how search engines actually see them. Google can’t magically understand what your picture shows unless you tell it properly. That’s where image SEO comes in, and frankly, it’s one of the most overlooked opportunities in the entire SEO game.

Think about it this way – every image on your site is a chance to rank in Google Images, drive traffic, and improve accessibility. Yet most websites treat images like afterthoughts. They upload massive files with names like “IMG_1234.jpg” and wonder why their pages load slowly.

Why Image SEO Actually Matters

Google Images gets over 1 billion searches per month. That’s not some tiny corner of the internet we’re talking about. People actively search for images, and those searches can lead directly to your website. But here’s what really gets me excited about image SEO – it’s still relatively easy compared to traditional SEO.

When you optimise images properly, you’re solving multiple problems at once. Page speed improves because you’ve compressed files correctly. Accessibility gets better thanks to descriptive alt text. Search engines understand your content more clearly. Users with slow connections can actually load your pages.

It’s like killing four birds with one stone, except nobody gets hurt and your website performs better.

The technical side matters too, though I’ll spare you the boring details. Search engines use images as context clues for your entire page. A well optimised image can actually boost the rankings of the text around it. Weird but true.

Alt Text That Actually Works

Alt text drives me slightly mad because everyone gets it wrong. They either skip it entirely or write completely useless descriptions like “image” or “photo”. Some people stuff it with keywords until it reads like spam. Neither approach works.

Good alt text serves two masters – screen readers and search engines. When someone using assistive technology visits your site, their screen reader announces what each image shows. If your alt text says “red Ferrari convertible parked outside modern office building”, they get the full picture. If it says “car image”, they get basically nothing.

Search engines appreciate descriptive alt text for similar reasons. They’re trying to understand what your image shows and how it relates to your content. The more context you provide, the better they can categorise and potentially rank your image.

Here’s my approach – describe the image like you’re talking to someone on the phone who can’t see it. What would they need to know? Skip obvious phrases like “image of” or “picture showing” because screen readers already announce it’s an image.

For a screenshot of Google Analytics, don’t write “Google Analytics screenshot”. Try “Google Analytics dashboard showing 45% increase in organic traffic over three months”.

Length matters too, though not in the way you might expect. Screen readers typically cut off alt text around 125 characters. That doesn’t mean you need to hit exactly 125 every time, but it’s a decent target. Sometimes you need more space to properly describe complex images. Sometimes less is more.

Filename Strategies That Search Engines Love

Your image filenames are probably terrible. Sorry, but someone had to say it. Files named “DSC_0001.jpg” or “untitled.png” tell search engines absolutely nothing. They’re wasted opportunities wrapped in digital packaging.

Good filenames work like mini SEO signals. When Google crawls your site, it examines everything – including what you’ve named your files. A filename like “chocolate-chip-cookies-recipe.jpg” immediately communicates what the image contains. It’s simple but effective.

I follow a few basic rules when naming image files. Use descriptive words separated by hyphens rather than underscores or spaces. Keep it concise but specific. Include your target keywords if they naturally fit, but don’t force it.

Think about someone searching for exactly what your image shows.

File extensions matter more than people realise. JPEG works best for photographs and complex images with lots of colours. PNG handles graphics, logos, and images with transparency beautifully. WebP offers the best compression but isn’t supported everywhere yet (though that’s changing rapidly).

One thing that genuinely annoys me – people who upload images straight from their camera without renaming them. Your website visitors don’t care that you took the photo on 15th March with your Canon camera. They care about what the image actually shows.

Compression Without Compromise

Large image files are website killers. They slow down page loading, frustrate users, and hurt your search rankings. Google has made page speed a ranking factor, so oversized images literally cost you traffic.

The trick is finding the sweet spot between file size and visual quality. I’ve seen websites with 5MB header images that could easily be 200KB without any noticeable difference in appearance. That’s 25 times smaller for essentially identical results.

Most image editing software offers quality settings when you export files. For JPEG images, I usually start around 80% quality and adjust from there. Sometimes you can drop to 60% for web use without obvious quality loss. PNG files benefit from tools that strip unnecessary metadata and optimise colour palettes.

Your goal should be keeping images under 100KB whenever possible.

There are tons of online compression tools that make this process painless. TinyPNG, ImageOptim, and Squoosh all do excellent work. Some content management systems handle compression automatically, though the results vary wildly.

I think responsive images are worth mentioning here too. Why serve a 2000px wide image to someone browsing on a phone with a 375px screen? It’s wasteful and unnecessary. Modern websites should serve different image sizes based on the device being used.

File Formats Decoded

Choosing the right file format feels technical, but it’s actually quite straightforward once you understand the basics. Each format has strengths and weaknesses that make it suitable for different situations.

JPEG dominates photography and complex images. It uses lossy compression, meaning some image data gets discarded to reduce file size. For photos with thousands of colours, this tradeoff usually makes sense. You get reasonable quality at manageable file sizes. However, JPEG struggles with graphics containing sharp edges or text because the compression creates visible artifacts.

PNG excels at graphics, logos, and any image requiring transparency. It uses lossless compression, preserving every pixel of the original image. The downside is larger file sizes, especially for photographs. PNG works brilliantly for simple graphics with few colours but becomes inefficient for complex photos.

WebP represents the newer generation of image formats. It provides better compression than both JPEG and PNG while maintaining excellent quality. The catch is browser support, though most modern browsers handle WebP perfectly well now.

SVG deserves mention for vector graphics and simple illustrations.

Since SVG files contain mathematical descriptions rather than pixel data, they scale to any size without quality loss. Perfect for logos and icons that need to look sharp on everything from phones to massive monitors.

When to Use What

Photos and complex images almost always call for JPEG. Logos, graphics, and images needing transparency work better as PNG. If you’re feeling adventurous and your audience uses modern browsers, WebP offers the best of both options.

Image Dimensions & Responsive Design

Getting image dimensions right prevents layout shifts and improves user experience. There’s nothing quite as annoying as a webpage that jumps around while images load, pushing content up and down unpredictably.

Modern web development practices suggest specifying width and height attributes for all images. This tells the browser how much space to reserve before the image actually loads. Your page maintains its layout even on slow connections.

Responsive design complicates things slightly because images need to work across different screen sizes. The old approach of creating separate mobile and desktop versions has largely been replaced by flexible images that scale smoothly. CSS can handle most of the heavy lifting here, but you still need to provide appropriately sized source images.

I generally recommend having images at least twice the width of their display size to accomodate high density screens.

Retina displays and similar high density screens pack more pixels into the same physical space. An image that looks crisp on a standard monitor might appear blurry on a modern smartphone or laptop screen. Planning for this from the start saves headaches later.

Aspect ratios matter too, though they’re often overlooked. Consistent aspect ratios create cleaner, more professional looking layouts. They also prevent awkward cropping when images get resized for different contexts.

Technical Implementation Tips

Getting the technical details right separates good image SEO from great image SEO. These aren’t the most exciting aspects, but they make a real difference in how search engines and users experience your images.

Structured data can provide additional context about your images. Schema markup tells search engines specific information about what images contain, who created them, and how they relate to your content. It’s not always necessary, but it can help in competitive niches.

Image sitemaps deserve consideration for sites with lots of visual content. They help search engines discover and index images that might otherwise be missed. Most SEO plugins handle this automatically, but it’s worth checking that your images are actually being submitted to search engines.

Loading lazy images improves page performance by only loading images when users scroll near them. This reduces initial page load times and saves bandwidth for people who don’t scroll through entire pages. Most modern browsers support lazy loading natively now.

Content Delivery Networks (CDNs) can dramatically improve image loading speeds.

By serving images from servers geographically closer to your users, CDNs reduce loading times and improve user experience. Many hosting providers include CDN services, or you can use dedicated services like Cloudflare.

Image placement within your HTML also influences SEO value. Images positioned near relevant text content get more contextual weight than images stuck in sidebars or footers. Search engines try to understand the relationship between images and surrounding text, so logical placement helps.

Common Mistakes to Avoid

After years of working with websites, I’ve seen the same image SEO mistakes repeated countless times. They’re usually innocent oversights rather than deliberate errors, but they still hurt performance.

Keyword stuffing in alt text remains surprisingly common. People cram their target keywords into alt text without considering whether it actually describes the image. This creates terrible user experiences for people using screen readers & provides little SEO benefit. Search engines have gotten much better at detecting and penalising obvious keyword stuffing.

Using images as the only source of important text information creates accessibility nightmares. If your contact details, prices, or key information only appear in images, screen readers can’t access them. Search engines also struggle to extract and understand text embedded in images.

Decorative images with unnecessary alt text add noise for screen reader users. Not every image needs alt text – purely decorative images should have empty alt attributes (alt=””) so screen readers skip them entirely.

Copyright violations happen more often than they should.

Using images without proper licensing can result in expensive legal problems. Stock photo sites, Creative Commons, and original photography are safer options than grabbing random images from Google searches.

Ignoring image performance on mobile devices is becoming increasingly problematic as mobile traffic dominates. Images that look perfect on desktop computers might be barely usable on smartphones. Testing your images across different devices and connection speeds reveals problems you might otherwise miss.

The Bottom Line

Image SEO isn’t rocket science, but it does require consistent attention to detail. Every image you upload is an opportunity to improve your site’s performance, accessibility, and search rankings. The question is whether you’ll take advantage of those opportunities or let them slip by.

I find it genuinely frustrating how many websites ignore these fundamentals. It’s not difficult work, and the tools are readily available. What’s missing is usually just awareness that image SEO matters and knowledge of what actually works.

Start with the basics – descriptive filenames, compressed file sizes, and useful alt text.

These changes alone will put you ahead of most websites. From there, you can experiment with newer formats, advanced compression techniques, and technical implementations.

Remember that image SEO serves real people, not just search engines. The best optimised image in the search results means nothing if it doesn’t actually help users accomplish their goals. Focus on creating genuinely useful, accessible, and fast loading images. The SEO benefits will follow naturally.