Quick answer
For image SEO: give each image a descriptive file name and meaningful alt text, serve the smallest file that looks good (WebP or AVIF where your toolchain supports them, otherwise optimised JPG or PNG), resize to the largest size actually displayed, set explicit width and height to avoid layout shift, and lazy-load images below the fold. FreeImageKit compresses, converts and resizes locally before upload.
Steps
- Name the file for what it shows, such as red-running-shoes.jpg, and write alt text that describes it for someone who cannot see it.
- Resize to the largest displayed size, then compress or convert to WebP with FreeImageKit.
- Add width and height attributes, lazy-load below-the-fold images, and keep the main (largest) image above the fold unlazy.
File names and alt text
Descriptive file names and alt text help search engines and assistive technology understand an image. Describe what is in the picture in plain language, avoid keyword stuffing, and leave alt empty for purely decorative images.
Format and compression
JPG suits photos, PNG suits transparent graphics and screenshots, and WebP or AVIF often produce smaller files at similar quality. Test AVIF and WebP in the browsers and CMS you actually use, and keep a fallback where needed. See the format comparisons for trade-offs.
Dimensions and layout shift
Serve images close to the size they are displayed, accounting for high-density screens when it matters. Setting width and height attributes lets the browser reserve space, which prevents content from jumping as images load and protects your layout-shift score.
Lazy loading and the main image
Lazy-load images below the fold so they do not compete with critical content. Do not lazy-load the largest image visible on first load, because delaying it hurts loading performance.
Frequently asked questions
Does image size affect SEO?
Indirectly. Heavy images slow page loading, which affects user experience and Core Web Vitals, and a better experience supports search performance.
Should I use WebP or AVIF?
Both usually give smaller files than JPG or PNG. WebP has broad support, and AVIF can be smaller but encodes slowly. Test with your own images and keep fallbacks where your tooling needs them.
Is it safe to compress images before uploading them?
Yes, and doing it locally means the originals are never sent anywhere. Keep your uncompressed originals for future edits.
Try the related local tools
Keep reading
Last updated
This guide describes format behaviour and product capability, not a guarantee for every source image or third-party workflow. Keep your original files and verify important exports.