Three drives full of music, six format choices on the same album, and no clear answer to "what should I save as?" That is where most people land after their first download tool gives them an option list. The wrong pick wastes either disk space or audio quality, and unwinding the choice later means re-downloading hundreds of tracks.
The right format depends on one variable: what you plan to do with the file. Below is the decision tree, then the reasoning, then the edge cases nobody covers.
§.01 — The problem
A 4-minute song lands at three very different sizes depending on format: about 4 MB as MP3, about 20 MB as FLAC, about 40 MB as WAV. Multiply by a 2,000-track library and the spread is 8 GB versus 80 GB. That is the storage cost of guessing wrong.
On the audio side, the gap is more subtle. MP3 throws away frequencies the encoder believes you cannot hear. FLAC and WAV throw away nothing. Whether the difference is audible depends entirely on what produced the file in the first place — and on what you are listening through.
§.02 — The solution, in three branches
Pick MP3 if the file will be played and not edited
Phones, car stereos, DJ controllers from before 2015, smart speakers — they all play MP3 without any setup. A 128 to 320 kbps MP3 sounds indistinguishable from the original to most listeners on most consumer hardware. Disk usage stays low, sync to a phone is fast, and the file plays anywhere with zero friction. This is the right pick for 90% of personal music libraries.
Pick WAV if the file will go into a DAW
Logic, Ableton, Pro Tools, Reaper, Audacity — every DAW reads WAV natively without a decode step. If the file is going to be sliced, layered, time-stretched, or pitch-shifted, WAV avoids the small fidelity loss that comes from re-decoding compressed audio every time the project loads. The trade-off is size and the fact that WAV cannot store cover art or proper tags. Acceptable when files live inside a project folder, painful when they live in iTunes.
Pick FLAC if you want lossless storage at half the size
FLAC compresses lossless audio to roughly 50% of the WAV equivalent. Bit-for-bit, the decoded audio is identical to WAV. The format also handles tags and embedded artwork, which WAV does not. The catch: older devices and cheap car stereos do not always read FLAC. Modern phones, VLC, foobar2000, and most music libraries from 2020 onward handle it cleanly.
§.03 — Where the picture changes for SoundCloud audio
SoundCloud streams 128 kbps MP3 to free listeners on the web. Wrapping that decoded audio in a WAV or FLAC container does not improve the underlying quality — both contain the same 128 kbps audio in a much larger file. For a deeper explanation, see the SoundCloud audio quality breakdown.
The exception is when the artist enabled the "Download" button on their track page. Those files are usually the original master — MP3 320, WAV, or sometimes FLAC. Saving the artist's download in its native format and only re-encoding when needed preserves the highest-quality copy you can legally obtain.
§.04 — Three edge cases people hit
- A.
Re-encoding MP3 to FLAC. The FLAC will be lossless of the MP3, not of the original. Anyone telling you their FLAC files came from MP3s and "sound better" is wrong about the physics.
- B.
Streaming via Bluetooth. Bluetooth re-encodes audio at the link layer using SBC, AAC, or aptX. A FLAC file plays through Bluetooth as compressed audio anyway. The fidelity ceiling becomes the codec the headphones support, not the file format.
- C.
DJ software metadata. Rekordbox and Serato analyze cue points based on the file's audio fingerprint. Convert the same track from MP3 to WAV later and the cue points have to be redone — different file, different fingerprint, even if the audio sounds identical.
§.05 — A 90-second decision flow
Will this file leave your computer? If yes — phone, car, friend's USB stick — go MP3. Maximum compatibility, smallest size, no surprise format errors at the wrong moment. If no, keep going.
Will the file be edited inside a DAW? If yes, go WAV. The DAW reads the audio without a decode step, and the project sounds the same on Monday as it did on Friday. If no, keep going.
Do you want lossless storage with cover art and tags, on hardware made after 2020? Go FLAC. Half the size of WAV, identical audio, plays everywhere modern. If you are unsure whether your hardware reads FLAC, fall back to MP3 and stop second-guessing.
That covers about 95% of real cases. The remaining 5% — multitrack stems, surround formats, broadcast-grade interchange formats — are far enough into the weeds that the answer changes per studio, and the question is no longer "MP3, WAV, or FLAC."
§.06 — One mistake to avoid
The single most common error: starting in MP3, deciding "I want lossless," and re-encoding the whole library to FLAC. The new files are larger but no closer to lossless of the original — they are lossless of the lossy MP3. The only honest path to lossless is starting from a lossless source. If you cannot find one, the MP3 you already have is the ceiling.