How to Convert AIFF to MP3

AIFF files are usually uncompressed audio, which makes them large and awkward to share, upload or play on some devices. Converting them to MP3 gives you much smaller files that almost any player accepts. MP3 is a lossy format, though, so the conversion permanently discards some audio data. This guide shows how to turn AIFF into MP3 with reliable settings and how to confirm the result.

Before you start

Keep your original AIFF files. An MP3 cannot be turned back into the original audio, so work on copies or write the MP3 files to a separate folder. Make sure you have enough free disk space for the new files, although MP3 output will be far smaller than the source.

Decide where the conversion will run. Desktop tools such as ffmpeg, Audacity and Apple Music on a Mac process files on your own computer. Web-based AIFF to MP3 converters upload your audio to someone else's server. If the recordings are private, unreleased or contain voices of other people, read the service's file retention and privacy terms yourself before uploading, and do not assume files are deleted immediately.

• Have ready:
• The AIFF files (extensions .aif or .aiff)
• One conversion tool installed: ffmpeg, Audacity or Apple Music (macOS)
• A target bitrate, for example 320 kbps constant bitrate or a high-quality variable bitrate setting
• An empty output folder for the MP3 files

Step-by-step instructions

Choose your encoding settings

Bitrate controls the trade-off between size and quality. Constant bitrate (CBR) at 320 kbps is the highest standard MP3 setting and the safest choice when quality matters more than size. Variable bitrate (VBR) adjusts the bitrate to the content; in the LAME encoder, quality level 0 or 2 is commonly used for high-quality music. For speech, podcasts or voice memos, a lower bitrate is often acceptable.

Standard MP3 supports sample rates of 32, 44.1 and 48 kHz and at most two channels. If your AIFF was recorded at 88.2 or 96 kHz, or contains more than two channels, the tool will need to resample or downmix it. Picking 44.1 kHz for music sourced from 44.1 kHz material, or 48 kHz for audio tied to video, avoids unnecessary conversion steps.

Option 1: ffmpeg (Windows, macOS, Linux)

ffmpeg is a free command-line tool that reads most AIFF variants and encodes MP3 with the LAME library. Open a terminal in the folder containing your file and run one of these commands.

Constant 320 kbps: ffmpeg -i input.aiff -codec:a libmp3lame -b:a 320k output.mp3

High-quality variable bitrate: ffmpeg -i input.aiff -codec:a libmp3lame -q:a 2 output.mp3

To force a sample rate or stereo output, add -ar 44100 or -ac 2 before the output file name. ffmpeg will not overwrite an existing file without asking unless you add -y, which helps keep the process reversible.

To convert all AIFF files in a folder on macOS or Linux, run: for f in *.aif .aiff; do [ -e "$f" ] && ffmpeg -i "$f" -codec:a libmp3lame -q:a 2 "${f%.}.mp3"; done

In Windows PowerShell, the equivalent batch command is: Get-ChildItem .aif | ForEach-Object { ffmpeg -i $.FullName -codec:a libmp3lame -q:a 2 ($.BaseName + ".mp3") }

Option 2: Audacity

Audacity is a free audio editor and suits single files or cases where you want to trim, normalize or fix levels before export.

• Open or drag the AIFF file into Audacity.
• Make any edits you need, such as trimming silence or lowering gain if the audio peaks at full scale.
• Use the export command in the File menu and choose MP3 as the format. The exact menu wording differs between Audacity versions.
• Set the bitrate mode and quality, check the sample rate and channels, and choose the output folder.
• Review the metadata fields shown during export, then save.

Current Audacity releases include MP3 export. Older versions required a separately installed LAME encoder, so if MP3 is missing from the format list, updating Audacity is the simplest fix. For many files, Audacity's Macros feature can apply the same export steps to a batch, but ffmpeg is usually quicker for large folders.

Option 3: Apple Music on a Mac

If your AIFF tracks are already in your Apple Music (formerly iTunes) library, the app can create MP3 copies. First set the import encoder to MP3 and pick a quality level in the app's file or import settings. Then select the tracks and use the convert option in the File menu to create MP3 versions. The originals stay in the library alongside the new copies. Menu names have changed across macOS and iTunes releases, so look for the import settings and convert commands rather than relying on an exact path.

Check the output

Play each MP3 from start to finish, or at least listen to the beginning, the loudest passage and the end. Listen for distortion on peaks, a muffled or swirly sound on cymbals and reverb tails, and cut-off endings.

Confirm the technical details. Your file manager's properties panel or the command ffprobe output.mp3 shows the codec, bitrate, sample rate, channels and duration. The duration should match the original AIFF closely; a tiny difference can come from encoder padding. The file size should be noticeably smaller than the source.

Check tags and artwork in your usual player. Track names, artist and album information may or may not transfer depending on how the AIFF was tagged and which tool you used. Album tracks meant to play without gaps may show short silences between songs in players that do not read the encoder's gapless information.

Common problems and next steps

The tool will not open the file. Some files labelled AIFF are actually AIFF-C, which can contain compressed audio, or have a wrong extension. ffmpeg reads most of these variants; running ffprobe on the file shows what it really contains.

MP3 is not offered as an export format. Update the application, or in older Audacity versions install the LAME encoder it asks for. In Apple Music, the convert command creates whatever format is selected in the import settings, so switch the encoder to MP3 first.

The MP3 sounds distorted although the AIFF is clean. Masters that peak right at full scale can clip after lossy encoding. Lower the level slightly before encoding, for example with a small gain reduction in Audacity, and convert again from the original AIFF, not from the faulty MP3.

Sample rate or channel errors. Resample high-rate files to 44.1 or 48 kHz and downmix multichannel audio to stereo, using -ar and -ac in ffmpeg or the export options in your editor.

Tags or cover art are missing. Add -map_metadata 0 to the ffmpeg command to request that source metadata be copied, and use a tag editor to re-add artwork if it did not carry over.

An online converter rejects the upload or times out. Web services often limit file size or the number of files. A local tool avoids those limits and keeps the audio on your own computer.

Converting MP3 to AIFF. This works with the same tools, for example ffmpeg -i input.mp3 output.aiff, and is useful when an editor or device only accepts AIFF. It produces a much larger file but does not restore any detail lost during MP3 encoding, so keep the original AIFF masters whenever you have them.