Lossless vs Lossy Image Compression: What Is the Difference?
Lossless compression can reconstruct the same pixel data. Lossy compression discards some information for a smaller output. The practical choice also depends on content, format, transparency, and future editing.
Do not confuse two meanings
“Lossless” is a technical property: decoding can recover the same pixels. “Visually lossless” only means a viewer did not notice a difference in a particular context; zooming or another edit may expose it.
- PNG commonly serves lossless workflows.
- JPEG is lossy.
- WebP/AVIF can be lossy or lossless depending on mode.
Content that benefits from lossless output
Small type, icons, lines, transparent edges, pixel art, and files that need continued editing are sensitive. Lossless output avoids lossy halos and generational damage, but it is not guaranteed to be smaller.
Content that fits lossy output
Photography and natural texture can tolerate controlled approximation. A one-time web, chat, or preview copy can often use high-quality JPEG/WebP/AVIF for substantially lower transfer.
- Encode once from a clean master.
- Lower quality gradually and inspect difficult regions.
- Do not promote the delivery output to the new master.
Use a two-layer file system
A master layer keeps RAW, TIFF, PNG, or a high-quality editable file. A delivery layer exports dimensions and formats for each destination. This gains transfer efficiency without losing the ability to rebuild.
References
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