How to name images for SEO (and write alt text that helps)

Images are one of the few places where you can give Google a plain-language hint and still get it right almost every time. Google can't fully "see" a photo — it reads the file name, the alt text, the surrounding copy, and the page speed. Get those four right and your images help the page rank; ignore them and they quietly slow it down instead.

Rule 1: name files before you upload them

IMG_4821.jpg tells Google nothing. golden-retriever-puppy.jpg tells it exactly what the image shows. The file name is the cheapest image signal there is — you set it once, before upload, and it never needs maintenance.

• Describe the image, not the article: sitemap-generator-tool.png, not how-to-make-a-screenshot-for-my-post.png.
• Use lowercase and hyphens, never spaces or underscores — hyphens are read as word separators, underscores are not.
• Keep it short — 3 to 5 descriptive words is plenty. very-long-file-name-with-every-keyword-i-can-think-of.jpg reads as spam to both Google and humans.
• No keyword stuffing — one accurate description beats five keywords glued together.

Rule 2: write alt text for people first, search engines second

Alt text exists so screen readers can describe images to blind visitors. That's its real job — and it happens to be exactly the description search engines want too. Write what a person would say if they briefly explained the image out loud:

• Good: "Meta tag generator showing a live Google search preview"
• Bad: "image", "screenshot1", or nothing at all
• Bad (stuffing): "meta tags SEO title description keywords free tool best 2026"

Keep it under about 125 characters — many screen readers cut off after that. If an image is purely decorative (a divider, a background texture), give it an empty alt attribute so screen readers skip it. And never put alt text on an image that is also a link without saying where the link goes.

Rule 3: compress before you upload

A 4 MB photo straight from a phone camera can triple how long your page takes to load — and slow pages rank worse and convert worse. Before uploading:

• Resize to the largest size it's actually displayed at. A 600px-wide content image doesn't need 4,000px of source.
• Use modern formats — WebP or AVIF typically cut file size by 25–50% compared to JPEG at the same quality.
• Aim for under ~200 KB per content image where you can.

Rule 4: put images near relevant text

Google reads the copy immediately around an image to confirm what it shows. An image of a sitemap tool sitting inside a section about sitemaps gets reinforced by its context; the same image dropped next to an unrelated paragraph gets weaker signals. Place images beside the text that discusses them, with a caption when it helps.

What about image sitemaps and lazy loading?

If images matter to your traffic (photography, products, infographics), list them in a dedicated image sitemap so Google discovers them faster. Use lazy loading with care: it's great for speed, but make sure the browser loads images as the reader scrolls rather than delaying everything — lazy loading that never fires is a common reason images never get indexed at all.

Try it yourself

Run your page through the free SEO Audit — it checks your images for missing alt text and reports overall page weight alongside title, headings, and structured data. To see how the rest of your on-page setup stacks up, read the Technical SEO checklist or work through the interactive SEO checklist.