How to convert AIFF to MP3 on a Mac
By Himanshu Ranjan · Updated 8 November 2026
Select the AIFF files in Finder, open FileDial, and run Convert › Convert to MP3. Each file gets a smaller MP3 copy beside it and the AIFF stays untouched. Nothing is uploaded. AIFF is uncompressed, so MP3 will save a lot of space at the cost of some audio detail.
Why AIFF files are so large
AIFF is Apple's uncompressed audio format, developed in 1988. Most AIFF files hold uncompressed PCM, and one minute of stereo at 44.1 kHz and 16-bit takes about 10 MB. A short session can run to hundreds of megabytes.
MP3 is lossy and far smaller, which makes it better for emailing, streaming from a website or fitting on a player. The price is that discarded audio detail cannot be recovered.
Convert with FileDial
- Select the .aiff or .aif files in Finder.
- Hold the right Option key to open the dial.
- Choose Convert › Convert to MP3 and release.
- The MP3 copies appear beside the originals. Undo removes them.
Use the Music app instead
For songs in your library, Music › Settings › Files › Import Settings, set Import Using to MP3 Encoder, then select the songs and choose File › Convert › Create MP3 Version. Apple lists AIFF among the formats Music works with. It is less convenient for loose files and sessions kept in folders.
Check your tags afterwards
AIFF can store metadata in its own chunks and can embed an ID3v2 tag. After converting, check the track title and artist in your player. Tags › Edit tags… writes a new copy with corrected tags, and empty fields keep what is already there.
Should you keep the AIFF
Yes, if it is a master. Lossy files are a poor starting point for later edits, since each re-encode adds loss. If you only want smaller files without going fully lossy, FileDial has Convert › Convert to FLAC and Convert › Convert to Apple Lossless, which keep the audio intact.
Choosing a bitrate mindset
MP3 supports bit rates from 32 to 320 kbit/s in MPEG-1, and 128 kbit/s is commonly used online. Higher rates keep more detail and make larger files. For spoken word, a modest rate is enough, and FileDial also has Compress › Compress for voice (64 kbps mono) as a separate step. For music, convert once with the general tool and judge by ear on your own speakers, since people differ on what they can hear.
If you need an exact bitrate for a platform, check its requirement first, because some distribution services accept only certain formats. For example, Apple's podcast guidance lists WAV, FLAC and MP3 for subscriber audio and MP3 or AAC for RSS feeds.
Handling a whole session or album
AIFF files often arrive as a folder of stems or takes, each of them large. Select the folder's files, run Convert › Convert to MP3 once, and then use Combine › Join tracks if you want a single track assembled in selection order. If the tracks need an even level before joining, run Edit › Normalize loudness on the copies first.
Finish by packing for delivery. Archive › Make ZIP or Combine › Make ZIP gathers the MP3s into one archive for sharing, and Archive › Deliverable package… adds a README and a SHA-256 manifest.
What happens to quality and to the files you keep
Going from uncompressed AIFF to MP3 is a single lossy step, which is the best case for MP3, because the encoder starts from the full recording. That is why people usually convert from the master rather than from an earlier MP3. If you have both, always convert from the AIFF.
Keep the AIFF as your archive, and treat the MP3 as disposable: you can always make another. If space is the pressure, back the AIFF masters up to an external drive before you delete anything from your Mac, and use Batch › Checksums (SHA-256) to write a checksum list, so you can later confirm that a copy matches.
When FileDial is and is not the right tool
FileDial suits loose files in folders and batches, because everything starts from a Finder selection. If your audio already lives in the Music app, its own File › Convert › Create MP3 Version is simpler, and If you need to specify an exact encoder setting for a delivery spec, check whether a dedicated audio editor exposes it, since FileDial's convert tool is a one-step conversion without per-file options.
A quick checklist before you batch convert
Pick one representative file and convert it first. Play it through on the speakers or headphones you normally use, and compare it with the AIFF at the same volume. Check that the duration matches, that the tags look right, and that nothing was clipped. Then convert the rest. Afterwards, sort the folder by kind so the MP3s and AIFFs are easy to tell apart, and move the MP3s to a separate folder before you copy them anywhere. If the AIFFs came from a project, keep them with the project files, since an MP3 is a poor source for any later remix or re-export.
Private by design
Recordings in AIFF are often studio work or interviews. FileDial runs every tool on your Mac and never uploads a file, and all tools work with Wi-Fi off.
Questions
Is AIFF better quality than MP3?
AIFF stores uncompressed audio, so it keeps everything that was recorded, while MP3 discards some detail to save space. Many listeners cannot tell a good MP3 from the original, but AIFF is the better master and editing format. Many listeners cannot hear the difference on everyday speakers, but the AIFF remains the safer choice for masters and later edits.
What is the difference between .aif and .aiff?
Nothing in practice. Both extensions mean the same Audio Interchange File Format. Standard AIFF uses .aiff or .aif, and compressed AIFF-C prefers .aifc. FileDial's Convert › Convert to MP3 works from the AIFF files you select in Finder. Either extension holds the same kind of audio, so FileDial's converter will accept both when you select the files in Finder.
Can I convert AIFF to MP3 in bulk?
Yes. Select the whole folder's files in Finder and run the tool once. FileDial processes the selection and writes an MP3 next to each AIFF, so you can convert a whole session export in one go. A whole folder works in one go, and sorting the results by name afterwards makes it easy to compare each MP3 with its AIFF source.
Is there a lossless way to shrink AIFF?
Yes. Convert to FLAC or Apple Lossless. Both compress without discarding audio data, so the result decodes to an identical copy. FileDial offers both under Convert. FLAC and Apple Lossless typically save space compared with AIFF while decoding to an identical copy, which is the better answer if quality matters.