What is Image Compression?
Image Compression is the process of reducing the file size of digital images by removing redundant or less important data, using either lossless methods (preserving all data) or lossy methods (sacrificing some quality).
Quick Facts
| Created | 1992 (JPEG standard) |
|---|---|
| Specification | Official Specification |
How It Works
Image compression reduces the storage and bandwidth requirements of digital images through mathematical algorithms that eliminate redundancy. Lossless compression (PNG, GIF, WebP lossless) preserves every pixel exactly, making it ideal for graphics, logos, and images requiring repeated editing. Lossy compression (JPEG, WebP lossy) achieves much smaller files by discarding visual information that humans are less likely to notice—typically high-frequency details. The quality-size tradeoff is adjustable; JPEG quality settings range from 0-100%. Modern formats like WebP and AVIF offer superior compression ratios compared to older formats. Image compression is essential for web performance, as images often constitute the largest portion of page weight. Best practices include choosing the right format for content type (JPEG for photos, PNG for graphics), using responsive images, and leveraging modern formats with fallbacks.
Key Characteristics
- Two types: lossless (exact) and lossy (approximate)
- Lossy achieves smaller sizes with quality tradeoff
- Different formats optimized for different content
- Quality settings control compression level
- Critical for web performance optimization
- Modern formats (WebP, AVIF) offer better compression
Common Use Cases
- Website optimization for faster load times
- Reducing storage costs for image hosting
- Email attachment size reduction
- Mobile app asset optimization
- Social media image preparation
Example
Loading code...Frequently Asked Questions
What is the difference between lossy and lossless image compression?
Lossless compression preserves all original image data and allows perfect reconstruction of the original file, but produces larger files. Lossy compression permanently removes image data that humans are less likely to notice, achieving smaller files but with some quality loss that cannot be recovered.
Which image format should I use for photos on the web?
For web photos, use JPEG or WebP with lossy compression at 80-90% quality for the best balance of file size and visual quality. WebP typically produces files 25-35% smaller than JPEG at equivalent quality. AVIF offers even better compression but has less browser support.
Why do my compressed images look blurry?
Blurriness occurs when using lossy compression with too low a quality setting. JPEG compression removes high-frequency details first, causing soft edges and artifacts. To avoid this, use higher quality settings (80-90%) or switch to lossless formats like PNG for images requiring sharp details.
Does compressing an image multiple times reduce quality further?
Yes, for lossy formats like JPEG, each save/compression causes additional quality loss as the algorithm discards more data each time. This is called 'generation loss.' Always work from original files and compress only once for final output. Lossless formats like PNG don't have this issue.
How much can I compress an image without noticeable quality loss?
For JPEG photos, 80-90% quality typically provides significant file size reduction with minimal visible quality loss. Below 70%, artifacts become noticeable. The optimal setting depends on image content—photos with smooth gradients show compression artifacts more easily than those with complex textures.