FLAC to MP3.

Yes, and there is no version of it that does not — that is what lossy means. What you can control is how much: 320 kbps from a genuine lossless source is about as good as an MP3 gets, and on a club system almost nobody can pick it out of the FLAC. What does audible damage is doing it twice, so always encode from the FLAC rather than from another MP3.

320, and it is not really a debate. The difference between 320 and 256 is small; the difference between 320 and 192 shows up on a big system as a dull, glassy top end exactly where a hi-hat lives. A four-minute track at 320 is about 9 MB, which means a 64 GB stick holds thousands of them — the space you save at a lower bitrate buys you nothing you need.

Yes. Artist, title, album, genre, year, label, BPM, key, comment and cover art are read off the source and written into the output, so a converted folder lands in Rekordbox named rather than as a wall of filenames. What does not come across is anything a DJ program keeps in its own private frames — Serato's cue points and beat grid in particular — because those live in an undocumented block that nothing outside Serato reads.

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 MP3 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 MP3, 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.