Lossless vs Lossy Compression: What You Keep and What You Lose
A plain explanation of lossless and lossy compression across images, audio and video, with examples and guidance on when each matters.
Two ways to make files smaller
Compression reduces file size by finding redundancy. Lossless methods remove only redundancy that can be restored perfectly. Lossy methods go further by discarding information that people are unlikely to notice, such as very fine colour variation in images or inaudible frequencies in sound.
| Media | Lossless | Lossy |
|---|---|---|
| Image | PNG, lossless WebP, TIFF | JPG, lossy WebP, AVIF, HEIC |
| Audio | FLAC, ALAC, WAV (uncompressed) | MP3, AAC, Ogg Vorbis |
| Video | FFV1, ProRes (high bitrate) | H.264, H.265, VP9, AV1 |
Generation loss
Every time a lossy file is opened, edited and saved again, more detail is discarded. A JPG re-saved many times shows blocky artefacts. To avoid this, edit from a lossless or original source and export once to a lossy format.
When lossless matters
Choose lossless for masters, archives, scientific images, graphics with text and anything you intend to edit repeatedly. Lossless files are larger, so they are poor choices for web pages and email attachments.
When lossy is fine
For viewing and sharing, high quality lossy compression is usually indistinguishable from the original and reduces size by five to twenty times. The key is to set a sensible quality level rather than the lowest possible one.
Converting between them
Converting lossy to lossless, for example MP3 to WAV, makes the file bigger but does not restore lost detail. Convert from the best available source whenever possible.
Frequently asked questions
Is ZIP lossless?
Yes. Unzipping returns the original files exactly.
Can I improve a JPG by converting it to PNG?
No. Converting to PNG preserves the JPG as it is, including its existing loss, but cannot bring back detail.
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Last updated 9 October 2026. Written by ARTH, a design and build studio in Coimbatore.