1Upload the M4A audio files you want brought to a consistent level — a whole set at once is exactly the case this is for.
2Pick a target: about -14 LUFS for streaming platforms, -16 LUFS for podcasts, -23 LUFS for broadcast.
3Run the analysis; integrated loudness and true peak are measured before any gain is decided on.
4Download the normalized M4A file, with the dynamics inside each track left untouched.
Normalize M4A Loudness FAQ
How does Normalize M4A Loudness decide the right level?
+
Concretely, loudness is measured against the EBU R128 standard and a single gain adjustment brings the whole file to the target LUFS — which is what streaming platforms actually measure, and is not the same thing as peak normalisation. The file is measured first and the correction follows from the measurement, rather than a fixed gain being applied and hoped for.
What is the difference between this and just turning it up?
+
A volume change applies a number you chose. Normalisation measures how loud the file actually is and computes the gain needed to hit a target, so ten files recorded at ten different levels all arrive at the same one.
Does the source format affect normalisation?
+
It does. M4A is an MP4 container holding AAC or ALAC audio — the default for iTunes and Apple Music files. That determines whether the corrected audio can be written back exactly or has to be re-encoded.
Anything specific to M4A here?
+
Yes — an .m4a can hold either AAC or ALAC, so lossy and lossless files share one extension and have to be told apart by inspection. Worth knowing when the goal is a consistent set rather than one file.
What loudness target should I aim for?
+
About -14 LUFS is what the major streaming platforms normalise to, -16 LUFS is the usual podcast target, and -23 LUFS is the broadcast standard. Going louder than the platform target gains you nothing — the platform simply turns it back down.
Does normalisation compress the dynamics?
+
No. It is a single gain adjustment for the whole file, so the relationship between the quiet and loud parts is untouched. Compression and limiting are separate operations and are not applied here.
What can I upload to Normalize M4A Loudness?
+
MP3, AAC, M4A, OGG, Opus and WMA are the lossy codecs handled directly, and lossless sources (WAV, FLAC, AIFF) can go in the same batch. The codec is probed from the stream, so an incorrectly named file still works.
Is there a file size limit on Normalize M4A Loudness?
+
Yes: free accounts process audio up to 200 MB per file, which at typical bitrates is several hours of material; ffmpeg does the decoding and encoding, exactly as it would on a desktop. That is the most generous cap on the site after video, and audio work rarely runs into it.
Will Normalize M4A Loudness lower the quality of my M4A audio files?
+
A lossy file has already discarded detail once, and re-encoding discards more — that is generation loss and it does not undo. Wherever the job can be completed by copying the encoded stream rather than re-encoding it, that is what happens, and the audio comes back bit-identical.
Can I run Normalize M4A Loudness on several M4A audio files at once?
+
Yes. Upload the set and they process in parallel with the same settings, which is the practical way to handle a podcast series or an album rather than repeating the job by hand.
Do tags and cover art survive?
+
Yes. ID3, Vorbis comments and MP4 metadata atoms are carried across, cover art included, so a processed file still sorts correctly in a music library. ReplayGain values are recalculated rather than copied, because a stale one is worse than none.
Does Normalize M4A Loudness cost anything?
+
No. Normalize M4A Loudness is free without an account and adds no audio watermark or spoken tag to the output. Your upload is deleted from the workers shortly after the job completes.
