Glossary
Image Compression
Also: image file compression · compressing images
Image compression reduces an image file's size by removing redundant or imperceptible data. Two methods exist: lossy compression discards detail for much smaller files, and lossless compression shrinks files with no quality loss.
Reviewed by Chad Solomon · Updated June 2026
Explained
How image compression works
Image compression encodes pixel data more efficiently than storing every pixel raw. Lossless methods (PNG, GIF) find and pack repeated patterns, so the decoded image is identical to the original. Lossy methods (JPG, WebP, AVIF) also discard fine detail the human eye barely notices, reaching far smaller files at a small, usually invisible, quality cost.
Explained
Why compression matters
Smaller images load faster, use less bandwidth, and rank better on page-speed metrics. A typical 4 MB phone photo compresses to roughly 400–800 KB as a JPG with no visible difference. The trade-off is control: over-compressing introduces blocky artifacts and blurred edges.
Put it to use
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Questions
Frequently asked
- Does compressing an image reduce its quality?
- Lossy compression (JPG, WebP) reduces quality slightly, though usually invisibly. Lossless compression (PNG) reduces file size with no quality loss at all.
- How do I compress an image without losing quality?
- Use lossless compression, or a lossy format at a high quality setting. convertimage's compress tool lets you balance size against quality in your browser.
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