FLAC vs. ALAC: Lossless Audio Quality, Compatibility and Conversion

FLAC and ALAC are both lossless audio codecs. They compress suitable digital audio so a decoder can reconstruct the encoded samples without the losses introduced by formats such as MP3 or AAC. If two files encode the same supported PCM samples and are decoded without alteration, their decoded audio samples should match.

The practical choice is usually about the apps, devices and workflows you use. FLAC commonly appears as a .flac file; ALAC, Apple Lossless Audio Codec, commonly appears in an .m4a container. An M4A extension alone does not prove that the audio is ALAC: it can also contain lossy AAC.

FLAC vs. ALAC at a glance

Question	FLAC	ALAC
Compression	Lossless for supported PCM input.	Lossless for supported PCM input.
Common file form	Often a native .flac file.	Often Apple Lossless audio in an .m4a file.
File size	Depends on the source and encoding settings.	Also varies with the source and encoder; compare actual outputs.
Playback	Supported by many apps and devices; verify the intended player.	Used by Apple’s lossless ecosystem and supported elsewhere; verify the intended player.
Source history	Lossless encoding cannot undo earlier lossy processing.	The same limitation applies to an ALAC copy.

RFC 9639 specifies FLAC’s lossless format. Apple describes ALAC as preserving the original encoded audio in its Music app documentation. The term “original” here means the audio supplied to the lossless encoder, not necessarily an untouched studio master.

Does one sound better?

If FLAC and ALAC versions decode to the same PCM samples and are played through the same unaltered signal path, the codec itself has not made one decoded audio stream different. Audible differences in a real comparison can instead arise from different masters, volume, processing, resampling, player settings or mismatched source files.

To compare specific files, first confirm their source, duration, channel layout, sample rate and bit depth. Decode both to the same PCM representation without resampling or processing, align them and use a bitwise or sample-level comparison in a suitable editor. A mismatch warrants investigation; it does not by itself prove that either lossless codec lost information.

A higher sample rate or bit depth is not proof that one file came from a better master. A lossy MP3 converted to FLAC or ALAC remains limited by the earlier encode. Read lossy vs. lossless audio for source-history examples.

Which file is smaller?

There is no universal winner. The source, sample format, encoder and settings affect lossless compression. Encode the same authorized source to both formats and compare the actual files; metadata and artwork can also affect file size. A smaller lossless output is not automatically lower audio quality if both decode to the same samples.

FLAC compression settings can change the amount of storage and processing required while remaining lossless for supported input. The FLAC project’s FAQ explains why the resulting bitrate varies with the source.

Which should you choose?

• Choose for the player: Test a short file in your actual device or library software. Check that it reads the codec, container, sample format and any tags you need.
• Choose for collaboration: Ask the recipient which files their editor accepts. A compatible PCM WAV may be useful as an interchange copy, but it does not improve a lossy source.
• Choose for archiving: Keep a verified, high-quality source and independent backups. Document the source and processing history rather than relying on an extension as proof.
• Keep metadata in mind: Tags, artwork and other non-audio information can be handled differently by tools. Lossless audio conversion does not guarantee identical metadata.

Can you convert between FLAC and ALAC without losing audio?

Yes, with a converter that supports both codecs and preserves the source’s sample rate, bit depth, channels and samples. The program decodes one lossless stream and encodes the resulting PCM in the other. Resampling, reducing bit depth, changing channels or applying gain can alter the audio even when the output codec is lossless.

1. Keep the original and check its properties. Note codec, sample rate, bit depth, channels and duration. Confirm that the conversion app accepts the source and can encode the intended output.
2. Choose the lossless destination. Select ALAC or FLAC explicitly; do not assume every M4A option is Apple Lossless. Preserve the original audio properties where the application allows it.
3. Convert to a separate file. Do not overwrite the source. Confirm the intended output codec and compare metadata and artwork in the destination.
4. Verify the result. Decode the source and output to the same PCM representation without processing, align them and compare samples with a suitable tool. Also listen to the beginning and end and test the file on the target player.

For files supported by Apple’s Music app, its conversion instructions describe choosing an import format and creating a separate version. Verify that your specific source is supported; Apple Music subscription downloads and protected files can have different restrictions.

Saturalabs’ FLAC-to-WAV converter decodes a supported short local FLAC and verifies its embedded audio checksum before downloading PCM WAV. It does not encode ALAC or directly compare two files. Its supported input and output limits apply; use a dedicated compatible converter when ALAC is required.

FLAC, ALAC and WAV

FLAC and ALAC are compressed lossless codecs. WAV is a container that often holds uncompressed PCM, though WAV files can contain other encodings. A PCM WAV can be larger because it is not using lossless compression; a larger file is not automatically a higher-quality master. See FLAC vs. WAV for a focused comparison.

Common questions

Is every M4A file Apple Lossless?

No. M4A is a file extension associated with an MP4-family audio container, and it can hold different codecs including AAC or ALAC. Inspect the codec rather than assuming it from the extension.

Does converting FLAC to ALAC improve quality?

No. A properly configured lossless conversion can preserve the supported source samples; it does not add detail or undo earlier lossy encoding.

Can a lossless file sound different in two players?

Yes. Volume, processing, resampling, output devices and other playback settings can differ. Compare the same decoded audio through matched settings before attributing a difference to the codec.