Image SEO: Alt Text, File Names & Compression That Actually Rank

Images account for roughly half the weight of a typical web page, and they're one of the most neglected SEO surfaces. Done right, they earn traffic from image search, strengthen your page's topical relevance, and keep load times fast. Done wrong, they're anonymous multi-megabyte bricks slowing everything down. Here's the complete playbook.

Alt text: write what the image shows

Alt text exists first for people who can't see the image, and that's exactly how you should write it: describe what the image actually shows, in the context of the surrounding content. If the paragraph discusses rising organic traffic and the image is a chart, 'Line chart showing organic traffic doubling over six months' is perfect alt text — descriptive, specific, and naturally keyword-relevant.

• Be specific: 'Golden retriever catching a frisbee on a beach' beats 'dog playing'.
• Skip 'image of' and 'picture of' — screen readers already announce it's an image.
• Don't stuff keywords. Alt text that reads like a tag list hurts accessibility and looks manipulative.
• Add a title attribute too, based on the surrounding content — it's a small extra relevance signal.
• Purely decorative images get empty alt (alt="") so screen readers skip them.

File names and uniqueness

Rename files before upload: on-page-seo-audit-chart.webp tells Google something, IMG_4821.jpg tells it nothing. And avoid reusing the same image across many pages — unique images per page give each page its own shot at image-search traffic and signal original content rather than template filler.

Compression: the speed half of image SEO

Page speed is a ranking factor, and oversized images are its most common killer. Three habits cover most of it: serve modern formats (WebP or AVIF cut file size 30–70% versus JPEG at the same quality), resize to the actual display dimensions instead of letting the browser shrink a 4000-pixel original, and lazy-load images below the fold so they don't block initial render.

Where image SEO pays off most

E-commerce product pages, recipe sites, tutorials with screenshots, and local business pages see the biggest returns — anywhere searchers actively use image results to choose where to click. But even on a plain blog post, proper alt text and compression are table stakes: they make the page faster, more accessible, and more clearly about its topic. That combination never goes out of algorithm fashion.