Convert MP3 to FLAC
Drop an MP3 and download a FLAC file at the same sample rate and channel count. FLAC compresses the decoded audio without discarding any of it, so every later export from that FLAC starts from identical samples.
Lossless from this point forward
The conversion draws a line: the MP3’s losses stay, and nothing new is added. That is the honest use for this pair. A collection manager that sorts by codec, a mastering step that refuses lossy input, or an archive policy that requires lossless files will all accept the FLAC.
What it will not do is undo the MP3. There is no process, in this tool or any other, that reconstructs frequencies an encoder deleted.
Size expectations
FLAC typically lands around 60% of the same audio stored as WAV, which still means a large jump from the MP3 you started with. A 4-minute track near 5 MB as MP3 becomes roughly 25 MB as FLAC.
Long exports stream to browser disk storage when it is available, so duration does not drive memory use.