What is JPEG?
JPEG (Joint Photographic Experts Group) is a commonly used lossy compression method for digital images, particularly photographs. The format achieves significant file size reduction by discarding some image data that is less perceptible to the human eye.
Quick Facts
| Full Name | Joint Photographic Experts Group |
|---|---|
| Created | 1992 by Joint Photographic Experts Group |
| Specification | Official Specification |
How JPEG Works
JPEG was created by the Joint Photographic Experts Group committee in 1992. It uses discrete cosine transform (DCT) to convert image data into frequency components, then quantizes and encodes them. The compression level is adjustable, allowing users to balance between file size and image quality. JPEG excels at compressing photographs and complex images with smooth color transitions but is not ideal for graphics with sharp edges, text, or transparency. The format does not support animation or transparency.
Key Characteristics
- Lossy compression - some quality loss with each save
- Adjustable compression ratio (quality 1-100)
- Excellent for photographs and natural images
- Does not support transparency or animation
- Uses DCT-based compression algorithm
- Smaller file sizes than PNG for photographs
Common Use Cases
- Digital photography storage
- Web images and thumbnails
- Social media image sharing
- Email attachments
- Print-ready photographs
Example
JPEG Compression Quality Comparison:
Quality File Size Visual Quality
100% ~500 KB Excellent (minimal loss)
85% ~150 KB Very Good (recommended)
70% ~80 KB Good (noticeable artifacts)
50% ~40 KB Acceptable (visible artifacts)
20% ~15 KB Poor (heavy artifacts)
JPEG vs PNG for a 1920x1080 photo:
JPEG (85%): ~200 KB
PNG: ~3 MB
Best practices:
- Use 80-90% quality for web
- Use 100% for archival
- Avoid multiple re-saves (quality degrades)