AudioKit

M4A compressor

Shrink iPhone voice memos, Apple Music downloads and other M4A files. Keep the M4A (AAC) format, or switch to MP3 if the destination needs it.

  • Runs on your device
  • No upload
  • No sign-up
  • Free

Drop a M4A file to compress

Stays on this device: nothing is uploaded. You can also drag a file here or paste it.

How M4A compression works

M4A files almost always contain AAC audio, which is already efficient. Shrinking one means re-encoding the AAC at a lower bitrate. iPhone Voice Memos default to about 64 kbps mono AAC in “compressed” mode, or lossless ALAC, which is much bigger, if Audio Quality is set to Lossless.

If your memo is a lossless (ALAC) M4A, compressing to 64 kbps AAC makes it about 90% smaller with no audible change for speech. Songs at 256 kbps can go to 128 kbps AAC and still sound good, because AAC holds up better than MP3 at lower bitrates.

Other compressors: MP3 compressor · WAV compressor · any audio format. To understand the numbers, see what bitrate means.

Audio file size calculator

≈ 4.8 MB (192 kbps × 210 s ÷ 8)

Questions people ask

How do I make an iPhone voice memo smaller?

Open the memo here (share it to Files first), choose “By purpose → Voice / podcast”, keep M4A selected and press Compress. To make future memos small, set Settings → Voice Memos → Audio Quality to Compressed.

Is M4A smaller than MP3?

At the same bitrate they’re the same size, because size is bitrate × length. AAC in M4A sounds better than MP3 at the same bitrate, so you can use a lower bitrate for the same quality.

Will the compressed M4A still play on iPhone?

Yes. The output is AAC-LC in an MP4 container, which every Apple device and modern Android phone plays.

More tools on the bench