Audio Converter

Every audio format falls into one of two groups. Lossy formats, such as MP3, AAC, M4A, OGG, Opus, WMA and AMR, make files small by removing parts of the sound that listeners are unlikely to notice. Lossless formats, such as WAV, AIFF, FLAC and ALAC, keep every sample. WAV and AIFF store the sound uncompressed; FLAC and ALAC pack it more tightly, the way a ZIP file packs a document, and unpack it exactly when played.

Three rules follow from that. Converting lossless to lossless changes nothing about the sound, only the container and file size. Converting lossless to lossy gives a much smaller file with a small, usually inaudible loss. And converting lossy to anything cannot recover what was removed; going from MP3 to FLAC makes a large file that sounds exactly like the MP3. Each lossy-to-lossy conversion, such as M4A to MP3, loses a little more, so it is best done once, from the best source you have.

FLAC is a good example of a modern lossless format. It is free to use, widely supported and documented as an IETF standard in RFC 9639. Its key facts are below.

When you need full quality, for editing, mastering or a music archive, the choice comes down to where the file will live. The three cards compare the formats people ask about most; AIFF behaves much like WAV and is the usual pick in Mac recording software.

Whichever of the three you pick, you can convert between them later without any loss, since all of them store the same samples. The decision is about convenience, file size and which apps you use, not about sound quality.

Playing it anywhere. MP3 at the default 192 kbps is the no-surprises choice. Old car stereos, gym equipment, cheap speakers and web forms that accept audio nearly always take MP3. Voice memos from an iPhone arrive as M4A and are the most common file people convert for this reason, which is what M4A to MP3 is set up for.

Saving space without losing much. M4A and Opus sound better than MP3 at the same low bitrate, which makes them good for audiobooks, lectures and phones with little storage. Opus was standardized by the IETF in RFC 6716 and is widely used for internet calls and web audio.

Editing in a sound program. WAV, or AIFF on a Mac, at 24-bit. Every editor opens them, and saving them again does not lose anything. When you are done editing, convert the final mix to MP3 or M4A for sharing.

Large WAV recordings. Field recordings and studio sessions in WAV are large. Converting them to FLAC keeps every sample and makes the archive lighter, and WAV to MP3 is the quick route when a lossy copy for listening is enough.

Old phones and voice systems. AMR is the speech format of older mobile phones and some voicemail systems. WMA is for older Windows players that ask for it. M4R is the iPhone ringtone format. MIDI is a special case: it does not store sound at all but notes, so the tool transcribes the melody instead of converting the recording.

Bitrate applies to lossy outputs and runs from 64 to 320 kbps, which is also the highest rate MP3 allows. More bits keep more detail; the default of 192 kbps is comfortable for music, and 128 kbps or less is plenty for speech. Bitrate mode chooses constant or variable bitrate for MP3, M4A, AAC, OGG and Opus.

Sample rate is how many times per second the sound is measured. Keep Same as source unless a device asks for a specific rate: 44.1 kHz is the CD standard, 48 kHz is the norm in video, and 8 or 16 kHz is enough for telephone-quality speech. Raising the rate of a recording does not add detail. Channels can turn stereo into mono, which halves a lossless file and loses nothing when there was only one microphone.

Bit depth applies to WAV, FLAC, AIFF and ALAC. 16-bit matches a CD; 24-bit and 32-bit float leave headroom for editing, but converting a 16-bit source upward does not make it any better.

Start at and End at keep only a section during the conversion, and Normalize volume brings the loudness to a standard level so that files from different sources play at a similar volume one after another. Keep tags and cover art copies the title, artist, album and embedded cover to the new file.

This converter expects audio files. If your sound is inside a video, such as a recorded concert or lecture, the Video to Audio tool extracts it with the same format choices and lets you pick between several audio tracks. To make a file lighter without picking every setting yourself, Compress Audio accepts a target size in MB or KB and works out the bitrate for you.

A few inputs are worth knowing about. WebM audio recorded in a browser, MKA tracks taken from MKV files, CAF files from Apple apps, and older formats such as AU, RA, APE and WavPack are all accepted. AC3 and DTS tracks saved from films are on the input list as well. If a file is refused, check that it really is audio and not a video or playlist with an audio extension.

Batches of up to 20 files share one set of settings, which suits jobs like turning an album of FLAC files into MP3 for a phone or moving a folder of old WMA files to M4A. Mixed sources in one batch are fine; a WAV, an OGG and an M4A can all become MP3 together. If some files should get a different bitrate or format, run them as a separate batch.

Before converting a large collection, try two or three typical files first and listen to them on the device you will actually use, such as earbuds, a car or a laptop speaker. That catches problems like the wrong sample rate for an old player or a bitrate that is lower than you would like, before you repeat the mistake across hundreds of songs.

Keep the originals. Converting from lossless to lossy is a one-way street, and new formats and devices keep arriving. A FLAC or WAV master can be turned into whatever format comes next, while an MP3 copy only ever gets worse with each further conversion. Cloud storage or an external drive is a sensible home for the lossless masters, with the light copies on your phone.