Start with the final display size
The most common image performance mistake is uploading a file that is much larger than the space where it appears. A 3000 pixel product photo displayed at 600 pixels still costs bandwidth, memory, and rendering time.
Resize the image close to its real display size first, then compress it. This keeps quality decisions predictable because the compressor is working on the same dimensions users will actually see.
Choose the right format before compressing
JPEG works well for photos, PNG is useful for transparency and crisp interface graphics, and WebP often gives smaller files for web delivery. If the image includes transparency, avoid converting blindly to JPEG because transparent areas will become a flat background.
For favicons and app icons, generate the correct ICO sizes rather than relying on a single large image. Browsers and operating systems still request different icon sizes in different contexts.
Compress until the trade-off is visible
Quality settings are not universal. A busy photo can often tolerate more compression than a screenshot with small text. Preview the result at the size users will see, then compare file size, sharpness, gradients, and edges.
For SEO, smaller images can improve page experience, but unreadable screenshots or distorted product photos hurt trust. The goal is useful speed, not the smallest number at any cost.
Practical checklist
- Resize images to their real display dimensions.
- Use JPEG or WebP for photos and PNG for transparency.
- Compress screenshots carefully so text remains readable.
- Generate favicon sizes such as 16x16, 32x32, 48x48, and 64x64.
- Keep original files when you may need future edits.