Convert M4A to ALAC — Free Online Converter

M4A files can contain either AAC (lossy) or ALAC (lossless) audio. If your M4A already contains ALAC, there is nothing to convert — it is already in the target format. However, if your M4A contains AAC audio (such as iTunes Store 256 kbps purchases), converting to ALAC re-encodes the lossy audio into Apple's lossless codec. The result is a larger file that stores the AAC-decoded audio losslessly, but this does not recover any quality that was lost during the original AAC encoding.

The main practical reason is format standardization. If you maintain an ALAC library and receive M4A files encoded as AAC, you might convert them to ALAC for consistency in your library management. Some DAWs and audio tools identify ALAC vs AAC M4A files differently and handle them with different import pipelines. Note that converting AAC M4A to ALAC does not improve audio quality — it simply prevents further generational loss if the file will be decoded and re-encoded in future workflows.

FFmpeg decodes the AAC stream inside the M4A to PCM, then encodes using ALAC back into an M4A container. The result is an M4A file with ALAC codec instead of AAC. If the source already contains ALAC, a simple stream copy (container remux) is all that is needed. ALAC in M4A uses the same iTunes metadata atom structure as AAC in M4A, so all tags and artwork transfer seamlessly.