Images are usually the most neglected part of a page’s SEO, and also one of the easiest to fix. While most site owners spend real effort on titles, headings, and body copy, they’ll upload a photo straight from their phone with a file name like IMG_4832.jpg, leave the alt text blank, and never think about it again. That single oversight quietly costs you on three fronts at once: Google Images traffic you’re not capturing, page speed you’re losing to an oversized file, and accessibility you’re failing to provide for anyone using a screen reader. All three are fixable with the same small set of habits.
Why File Names Actually Matter
Before Google ever renders an image or reads its alt text, the file name itself is a signal. A file named IMG_7489.jpg tells a search engine nothing at all. A file named tropical-green-smoothie-recipe.jpg tells it exactly what the image shows, before a single pixel is analyzed. This is a confirmed, if modest, signal, and it costs nothing to get right beyond a habit change: rename every image descriptively before you upload it, using real words separated by hyphens rather than underscores or spaces, since Google reads hyphens as word separators and underscores as a single joined word. This is a one-time effort per image with a permanent, if small, benefit, and it’s worth doing as a matter of routine rather than an afterthought.
Writing Alt Text That Actually WorksAlt text is the single highest-impact image SEO habit most sites get wrong, and it serves two audiences at once: people using screen readers, who rely on it to understand what an image shows, and Google, which uses it as one of its primary signals for what an image depicts and which queries it should match. Good alt text describes what’s genuinely in the image, in plain, natural language, the same way you’d describe it to someone on the phone who couldn’t see it. For a product photo, that might mean including the brand, the color, and a distinguishing detail rather than a generic label like “shoe.” For an image supporting a specific point in an article, it means describing what the image is actually illustrating in that context, not a generic caption that could apply to any similar image anywhere on the internet.
The mistake to avoid is treating alt text as a place to stuff extra keywords. Alt text that reads as an unnatural list of search terms rather than a genuine description performs worse, not better, and it actively fails the accessibility purpose it’s meant to serve. If an image is purely decorative and adds nothing informational to the page, such as a background flourish or a stylistic divider, the correct choice is an empty alt attribute rather than a forced description, which tells screen readers to skip it entirely rather than reading out something meaningless.
Choosing the Right Format
Format choice is the single biggest lever for how much an image weighs on your page, and the landscape has genuinely shifted in recent years. WebP is now the universal baseline: it’s supported in every browser worth targeting, produces meaningfully smaller files than JPEG or PNG at equivalent visual quality, and supports transparency, which lets it fully replace PNG for most purposes. AVIF goes further still, often producing noticeably smaller files than JPEG, though encoding takes more processing time and a small amount of older browser support is still catching up. The safest, most future-proof approach is to serve AVIF as the primary format with WebP as a fallback and JPEG or PNG as a final fallback for anything unusual, using the HTML picture element to let the browser choose automatically. If your CMS or platform doesn’t yet support that layered approach, WebP alone as your default is still a strong, simple choice that covers the vast majority of the benefit.
Compression Without Losing Quality
Even in a modern format, an oversized file still hurts you. The common mistake is uploading a photo straight from a phone or camera at its full native resolution, several megabytes in size, and letting the browser scale it down visually while the full file weight still has to load. The fix is compressing images before upload and resizing them to the dimensions they’ll actually display at, rather than shipping a four-thousand-pixel-wide photo into an eight-hundred-pixel column. Free tools like Squoosh, or automated pipelines built into many CMS platforms, can apply lossy compression at a quality level high enough that there’s no visible difference, while cutting file size dramatically. As a rough target, aim to keep hero and above-the-fold images under a few hundred kilobytes and smaller supporting images well under that, adjusting for how visually complex the image actually is.
Preventing Layout Shift and Protecting Page SpeedTwo further technical habits round out the picture. First, always include width and height attributes on your image elements, or set an aspect ratio in your CSS, so the browser reserves the correct space for the image before it finishes loading. Skipping this is one of the most common causes of layout shift, where content jumps around as images pop in, which hurts both user experience and your Core Web Vitals score. Second, apply lazy loading to images below the fold, so the browser doesn’t waste time and bandwidth loading images the visitor hasn’t scrolled to yet, while making sure your single largest, most important image, typically a hero image, is not lazy loaded and is instead prioritized to load immediately, since that image is usually the one determining your page’s Largest Contentful Paint score.
Structured Data and Discoverability
Beyond the image itself, a small amount of structured data helps Google understand an image’s role on the page, particularly for product photography or a page’s primary representative image. This isn’t a requirement for most content, but it’s a genuinely low-effort addition for e-commerce pages specifically, where product schema including image properties can meaningfully affect how a listing appears in search. For a typical blog, getting the fundamentals right, descriptive names, honest alt text, an efficient format, and reasonable compression, covers the overwhelming majority of the available benefit.
Building This Into Your Workflow, Not Treating It as a Separate Project
The realistic failure mode isn’t not knowing these practices, it’s knowing them and still skipping them under deadline pressure, because none of them feel urgent in the moment a page gets published. The fix isn’t a one-time cleanup project, it’s building a habit: before publishing anything, take a moment to confirm every image has a real file name, a genuine alt description, a modern format, and a reasonable file size. Treating this as part of the normal publishing checklist, rather than a separate audit you’ll get to eventually, is what actually keeps a site’s image library in good shape as it grows, rather than accumulating the same oversight across hundreds of pages until a much larger cleanup becomes necessary.