Image SEO: Alt Text, File Names, and Compression

Images Carry More SEO Weight Than They Get Credit For

Images are often the last thing anyone thinks about when building a page — dropped in after the copy is written, named whatever the camera or download gave them, uploaded at whatever size they happened to be exported. That's a missed opportunity on two fronts: images are a legitimate source of search traffic in their own right through Google Images, and unoptimized images are one of the most common reasons a page loads slowly, which affects both rankings and conversion.

Alt Text: Not Just an SEO Trick

Alt text (short for alternative text) is a written description attached to an image in your page's HTML:

<img src="roof-repair-austin.jpg" alt="Roofer repairing shingles on a residential roof in Austin, TX" />

Its primary purpose is accessibility — screen readers used by visually impaired visitors read alt text aloud in place of the image, so someone using assistive technology understands what's on the page. It also displays as fallback text if an image fails to load. Its SEO value is a secondary benefit built on top of that primary purpose: alt text is one of the only ways search engines have to understand what an image actually depicts, since they can't reliably "see" the way a human does.

Good alt text is specific and descriptive, the way you'd describe the image to someone on the phone who can't see it. "Roofer repairing shingles on a residential roof in Austin, TX" tells you something real. "Image1234" or "roofing" tells you almost nothing. At the same time, don't overcorrect into keyword stuffing — "roofer roofing roof repair Austin roofing company" is neither accurate description nor good practice, and it can read as manipulative to search engines evaluating the page's overall quality.

Decorative images that add no informational value (a purely visual divider, for instance) can use an empty alt attribute (alt=""), which tells screen readers to skip them entirely rather than reading out something meaningless.

File Names: A Small Detail With Real Signal Value

Before an image is even uploaded, its file name is a piece of information search engines read. IMG_04829.jpg conveys nothing. austin-roof-repair-before-after.jpg tells a crawler what's likely in the image before it even processes the alt text or surrounding page content. This is a five-second habit to build into your upload process — rename the file with a short, descriptive, hyphenated name before uploading, rather than leaving whatever your camera or phone assigned.

This matters somewhat for standard web search, but it matters more directly for Google Images, which is a real, sometimes underestimated source of traffic for businesses in visual industries — real estate, home improvement, food service, product-based businesses, before/after work like detailing or landscaping. Someone searching "kitchen remodel before and after" in Google Images and clicking through to your site is a warm visitor who found you through a channel most competitors haven't bothered optimizing for.

Compression: The Speed Half of Image SEO

Alt text and file names help search engines understand images. Compression addresses a different problem entirely: unoptimized images are consistently one of the largest contributors to slow page load times, which is both a direct (if modest) ranking factor and a much larger factor in whether visitors actually stay on your page. See page speed and SEO for how that connection works in more depth.

A photo straight off a modern phone or camera can easily be 4-8MB. Displayed on a webpage at a few hundred pixels wide, almost none of that resolution is being used — the browser is downloading a huge file and then shrinking it down, wasting bandwidth and load time in the process. Compressing that same image can often bring it down to a few hundred kilobytes with no visible quality loss at the size it's actually displayed.

Practical Steps for Compression

• Resize before uploading. If an image will display at 800 pixels wide, there's no benefit to uploading a 4000-pixel-wide original — resize it first.
• Use a modern format. WebP typically produces meaningfully smaller file sizes than JPEG or PNG at equivalent visual quality, and is now supported by all major browsers. Many CMS platforms and image tools can convert automatically on upload.
• Compress, don't just resize. Tools like TinyPNG or Squoosh reduce file size through smarter encoding, independent of dimensions, often cutting file size substantially with no visible difference.
• Use lazy loading for below-the-fold images. The loading="lazy" HTML attribute (or an equivalent setting in most site builders) defers loading images until a visitor scrolls near them, so a page with twenty images doesn't force all twenty to download before the visitor sees anything.

On WordPress, plugins like Smush or ShortPixel automate compression on upload, which is worth having if you or your team regularly add new images without a developer double-checking file size each time. On a custom-built site, this is typically handled in the build pipeline — Next.js, for instance, has an image component that handles resizing, format conversion, and lazy loading automatically, which is one practical advantage of that kind of setup for image-heavy business sites.

A Realistic Habit, Not a One-Time Fix

Image SEO isn't a project you finish once — it's a habit that needs to hold up every time someone on your team uploads a new photo. The most common failure pattern isn't a site that never optimized its images; it's a site that got it right at launch and then slowly accumulated years of unoptimized uploads afterward as new content went up without anyone checking file size or writing alt text. If you're publishing images regularly — new products, new blog posts, new project photos — it's worth a quick periodic check: pull up your largest pages in Google PageSpeed Insights and see whether images are flagged as a load-time issue, and spot-check a handful of recent uploads for missing or lazy alt text like "image" or a blank field.

Individually, these are small details. Collectively, across a site with hundreds of images accumulated over years, they add up to a real difference in both how fast your pages load and how discoverable your visual content is.