Lossy vs Lossless Formats

What the two terms mean

Lossless compression reduces file size by removing redundancy while preserving every original bit. PNG, FLAC, ZIP, and FLAC-style audio masters are lossless. Lossy compression removes information that is difficult to perceive, which is how JPEG, MP3, and most video codecs stay small.

The key difference is round-tripping. A PNG saved and reopened always matches the source; a JPEG resaved at a lower quality loses a little more detail each time.

Where lossy makes sense

Lossy formats make sense when the final audience is human and the file must travel quickly. A website photograph, a podcast, or a streaming movie are all examples where a small size matters more than perfect fidelity.

Keep the quality setting high enough to avoid visible artifacts, and never use a lossy file as the master for further edits. Edit from the source, then export one compressed copy for delivery.

Where lossless matters

Lossless matters for anything that will be edited again, archived, or processed by software. Screenshots, UI assets, audio masters, CAD models, and source documents should stay lossless until the final delivery step.

A practical example: recording a podcast as MP3 and then editing it forces every cut to be decoded and re-encoded. Recording in WAV or FLAC keeps the production clean, and the final MP3 is created once at the end.

A simple test

Ask one question: would you notice or lose work if some information were discarded? If the answer is yes, use lossless. If the file is a final copy meant for playback or viewing, lossy compression is usually the right trade-off.