How to Optimize Images for SEO

Images often account for more than half of a page's weight. Optimizing them improves speed, accessibility and visibility in Google Images.

1. Choose the right format

• WebP or AVIF: modern formats, lighter at equivalent visual quality, well supported by current browsers.
• JPEG: for photos, when you are not using a modern format.
• PNG: for images that need transparency or sharp flat areas.
• SVG: for logos and icons, which stay sharp at every size.

2. Reduce file size

• Resize the image to the size actually displayed (no point sending 4000 pixels of width for an 800-pixel slot).
• Compress it with a suitable tool, checking that quality remains good.
• Use the srcset and sizes attributes to serve a size suited to each screen.

3. Take care of the file name

Prefer title-tag-example.webp to IMG_4521.jpg. A descriptive, lowercase name with hyphens gives extra context.

4. Write a good alt attribute

• Describe the image as you would to someone who can't see it.
• Stay concise and relevant to the page's content.
• Don't stack keywords: it is useless for screen readers and risky.
• Leave the attribute empty (alt="") for purely decorative images.

5. Set dimensions and load intelligently

• Set width and height to avoid layout shifts (CLS).
• Enable lazy loading (loading="lazy") for images below the fold.
• Do not lazy-load the main image that is visible on arrival, as it would slow down LCP.

6. Take care of the context

• Place the image near text that discusses it and add a caption when useful.
• Use real <img> tags for content images, rather than CSS background images, which Google can associate with the page less well.
• Prefer original, good-quality images over generic visuals.

Finally, check the result with PageSpeed Insights and verify in Search Console that your pages are indexed.