Compress Image

Image Compression Explained: Lossy vs. Lossless, Quality Settings, and Optimization

Image compression reduces file size by removing redundant or less-important data. Understanding the two types of compression helps you choose the right settings for every situation - whether you are optimizing a website, sending photos via email, or storing an archive.

Lossy vs. Lossless Compression

Understanding Quality Settings

JPEG quality is typically expressed as a number from 0 to 100. Here is what different ranges look like in practice:

• 90-100: Nearly indistinguishable from original. File is still 2-5x smaller than uncompressed.
• 75-89: Excellent quality. Most people cannot spot the difference. Best for web images.
• 50-74: Good quality with noticeable compression artifacts on close inspection. Good for thumbnails.
• Below 50: Visible artifacts, blocky patterns. Only for extreme size reduction needs.

The sweet spot for most web images is 75-85% quality. This provides a dramatic file size reduction (often 70-80%) with minimal visible quality loss.

When to Use Each Format

• JPEG: Photographs and complex images with many colors. Does not support transparency.
• PNG: Graphics, screenshots, text, logos, images needing transparency. Larger than JPEG for photos.
• WebP: Modern format that replaces both JPEG and PNG. 25-35% smaller at equivalent quality. Supported by all modern browsers.
• AVIF: Next-gen format with even better compression than WebP. Growing browser support.

Optimization Tips for Websites

• Serve the right size: Do not load a 4000px image in a 400px container. Resize to the display size first.
• Use responsive images: The HTML <picture> element and srcset attribute serve different sizes to different devices.
• Enable lazy loading: Add loading="lazy" to images below the fold so they only load when scrolled into view.
• Strip metadata: EXIF data (camera info, GPS location) can add 10-50 KB per image. Strip it for web use.
• Use a CDN: Content delivery networks cache and serve images from servers closest to the user.

For a step-by-step guide, read our comparison of the best image compressor tools. Need to resize first? Use the image resizer to hit the right dimensions before compressing.