Lossless vs lossy audio: which format should you keep?
By Himanshu Ranjan · Updated 8 November 2026
Lossless audio (FLAC, WAV, AIFF, Apple Lossless) keeps every detail and decodes to an exact copy, so it suits masters and editing. Lossy audio (MP3, AAC, Opus) discards detail to make small files, so it suits sharing and listening. Keep lossless originals, make lossy copies, and never re-encode lossy audio repeatedly.
The core difference
Lossless compression lets you rebuild the original data exactly. Lossy compression gives up exactness and reconstructs an approximation, usually in exchange for much smaller files. For audio, lossless formats are typically kept for archiving and production, and compact lossy files suit portable players and tight storage.
Lossless is not one thing. Uncompressed formats such as WAV and AIFF store the samples as they are. Compressed lossless formats such as FLAC and Apple Lossless make files smaller while decoding to an identical copy.
The formats at a glance
No table of numbers here, because file sizes depend on the audio. The facts that matter, from the sources below:
- WAV: published by IBM and Microsoft in 1991, usually uncompressed PCM, capped just under 4 GiB.
- AIFF: Apple's format from 1988, usually uncompressed PCM, about 10 MB a minute for CD-quality stereo.
- FLAC: open, lossless, with metadata and cover art, supported by macOS since High Sierra.
- MP3: lossy, 128 kbit/s common online, near-universal support, key patents expired by 2017 in the US.
- AAC: usually in .m4a files, generally better than MP3 at the same bit rate.
- Ogg Vorbis and Opus: open lossy formats, with Opus recommended by Xiph for new use. macOS has no native Vorbis support.
Can you hear the difference
It depends on the bit rate, the codec, the material, your equipment and you. At low bit rates artifacts are audible in many files, and at high rates many listeners cannot reliably tell. I will not quote a threshold, because the right test is your own: convert a track you know well and compare on the speakers you actually use. For speech, a modest lossy rate is usually fine.
A sensible workflow
Keep a lossless master of anything you recorded or bought in lossless. Edit in lossless, because each lossy save adds loss. Make lossy copies at the end for delivery. In FileDial that means Convert › Convert to FLAC or Convert › Convert to Apple Lossless for archiving, Convert › Convert to WAV or Convert › Convert to AIFF for editing and Convert › Convert to MP3 or Convert › Convert to M4A for sharing. Compress › Compress to 128 kbps and Compress › Compress by percentage… make smaller lossy copies.
Converting lossy to lossless does not restore anything. It only makes a bigger file with the same sound.
Metadata and cover art across formats
Format choice also affects tags. FLAC stores text tags as Vorbis comments and supports cover art. AIFF can store tags in its own chunks and can embed an ID3v2 tag. MP3 commonly uses ID3 tags. WAV is a chunk-based container, and tag support varies between players, which is a practical reason many people prefer FLAC or AIFF for tagged archives.
FileDial can check and fix these: Tags › Edit tags… writes a copy with corrected tags, Tags › Extract cover art saves the embedded picture, Combine › Add cover art attaches one without re-encoding, and Tags › Remove tags strips them.
Which one for which job
For a recording you made, keep a lossless master. For editing on a Mac, WAV or AIFF are straightforward, and Apple Lossless or FLAC save space. For sending to a client who plans to edit, send lossless. For playing on a phone, a lossy copy is fine, with AAC generally better than MP3 at the same bit rate. For video voiceovers or phone calls, Opus is built for speech. For old devices and car stereos, MP3 is the dependable choice.
One more rule: lossless is not a guarantee that a file is high quality. A lossless file made from an MP3 contains the MP3's flaws, so quality is decided at the first lossy step, not the last.
Storage planning in practice
A practical storage plan has three tiers. Masters, in a lossless format, on an external drive with a second copy elsewhere. Working files, in WAV, AIFF or FLAC, on your Mac while a project is active. Delivery copies, in MP3 or M4A, wherever they are needed. When a drive fills up, convert masters you rarely open from WAV or AIFF to FLAC or Apple Lossless, which keeps the audio intact and saves space, and delete delivery copies freely, since they can be rebuilt. Test restoring one file from backup occasionally, because an untested backup is only a hope.
Converting on a Mac, privately
The Music app converts library songs between AIFF, WAV, MP3 and AAC, and Apple warns that converting between compressed formats may reduce quality. FileDial does the same from Finder for loose files in batches. FileDial runs every tool on your Mac and never uploads a file, and all tools work with Wi-Fi off.
Questions
Is FLAC better than MP3?
FLAC is lossless, so it keeps the audio exactly, while MP3 is lossy and much smaller. FLAC is better for archives and editing, MP3 for compatibility and small files. Many people keep FLAC masters and MP3 copies. For most people the practical answer is lossless for the archive and a small lossy copy for everyday listening.
Does converting MP3 to WAV improve quality?
No. The detail an MP3 discarded is gone for good. WAV just stores the decoded audio without further compression, which helps editing and compatibility but makes a much larger file. The conversion cannot recreate detail that was thrown away, so you pay for the disk space without any gain in sound.
Which format should I use for podcasts?
Apple lists MP3 or AAC for RSS feed audio, and WAV, FLAC or MP3 for subscriber audio. Edit and master in lossless, then export one MP3 or AAC for the feed. Whichever format you choose, keep the loudness and channel settings consistent with what your host asks for.
What is the best way to shrink audio without losing quality?
Use a lossless format such as FLAC or Apple Lossless. They shrink files compared with WAV or AIFF and decode to an identical copy. FileDial offers both under Convert. Apple Lossless works well inside Apple software, while FLAC is open and widely supported, so choose by the devices you use.