FLAC to WAV.

Completely. FLAC is compression in the same sense a zip file is — it stores the audio more cleverly, not more cheaply — so unpacking it to WAV recovers the identical samples. You can convert back and forth as many times as you like and the audio never changes. This tool also writes a checksum into every FLAC it makes, so a file can prove years later that it is still the recording it started as.

Compatibility, and nothing else. WAV opens in everything ever written, including the sampler in an old groovebox and the DJ software that has not been updated since 2016. FLAC is the better format for storage — same audio, two-thirds the disk — so the sensible pattern is to keep FLAC and make a WAV when something refuses to read it.

AIFF. It is the same audio in a different container, it analyses at least as fast, and it holds artist and title tags reliably where WAV does not. The only reason to prefer WAV is that something downstream demands it.

No, and that is the main reason to use this rather than a site that asks you to wait for an upload. The FLAC is decoded, re-written as WAV and handed back entirely inside this browser tab — open the network panel and watch it stay empty. There is no server behind the page, which means an unreleased promo is safe to drop on it and nothing is sitting in somebody's bucket afterwards.

Yes. Drop as many files as you like, set the format once, and the whole queue is converted with a report for each file — what it came from, what it went to, and how the size compares. The results come back as a single archive rather than as thirty separate downloads, which is what you want when the next step is dragging a folder into Rekordbox.

Yes. Artist, title, album, album artist, genre, year, track number, label, remixer, composer, BPM, key, ISRC, comment and the cover art are all read off the FLAC and written into the WAV, so a converted folder arrives in Rekordbox named rather than as a wall of filenames. The one thing that does not travel is anything a DJ program keeps in its own private frames — Serato's cue points and beat grid live in an undocumented block that nothing outside Serato reads, and no converter can carry them.

Up to 800 MB per file, which is about 75 minutes of 24-bit stereo audio — a full recorded set fits comfortably. Past that it is the browser's own decoder that gives up rather than the tool.

The lossless formats are written here, and verified: every test file was decoded again by an independent decoder and compared sample by sample against the original, with zero differences. On real records the FLAC comes out at about 67% of the uncompressed size, which sits between the standard encoder's default setting and its slowest one. MP3 uses the reference encoder that has been the answer to that problem for twenty-five years, because a homemade one would not make bigger files, it would make worse-sounding ones.