Convert audio files between MP3, AAC and HE-AAC, M4A, FLAC, WAV, AIFF, ALAC, Opus and Ogg Vorbis, and read, edit or carry over their tags and cover art. Everything runs in your browser: the file is never uploaded.

Prefer it without the site around it? Open the Audio File Converter on its own page.

What it does

Detects the file: container, codec and profile (it tells AAC-LC, HE-AAC and HE-AAC v2 apart), sample rate, bit depth, channels, bitrate and length.
Reads and edits tags: title, artist, album, album artist, year, genre, track, disc, composer and comment, any other tag the file carries (ReplayGain, MusicBrainz IDs, …), and the cover art, which you can keep, replace or remove. A tag the chosen format cannot hold turns red, so nothing goes missing unnoticed. It can also fill tags in from the filename.
Converts to MP3 (VBR or CBR), AAC in M4A or raw ADTS (AAC-LC, HE-AAC, HE-AAC v2), Opus, Ogg Vorbis, FLAC, ALAC, WAV and AIFF, with a choice of bitrate or quality, sample rate, channels and bit depth, or one click on a preset.
Converts many at once: drop several files or a whole folder, edit what they share in one go, number the tracks, and download everything as one ZIP. A file that fails does not stop the rest.
Normalizes the level: a single gain change to −14, −16 or −23 LUFS, or the peak to −1 dBFS, so the dynamics stay as they are, or just ReplayGain tags with the audio left alone, measured per track or across a whole album.
Edits tags without re-encoding: when the target format is the source’s own (MP3 to MP3, FLAC to FLAC, AAC to M4A, …), the audio is copied bit for bit and only the tags change.
Lets you hear the quality first: it encodes 15 seconds with your settings and switches between that and the original in step, with an estimate of the final size.
Checks the result: the new file is read back before you download it, so what it reports is what you get.

Listening and checking

Every file can be played, even in a codec the browser cannot handle itself. Four more tools stay out of the way until you switch them on:

Waveform: see the whole file and click anywhere to jump there.
Trim and fade: drag the handles or type the times, add a fade in or out, or cut silent ends, and hear the result before converting.
Level meter: true peak, RMS, EBU R128 loudness and stereo correlation, live as the file plays.
Audio check: loudness, true peak, clipping, stereo and silent ends in plain words, with a spectrogram. It warns when a lossless file stops so sharply that it was probably made from a lossy one.

Which format should I pick?

To play anywhere: MP3 (VBR V0 is close to transparent) or AAC-LC in M4A at 256 kb/s.
Small files, streams, podcasts: HE-AAC at 48 to 64 kb/s, HE-AAC v2 at 24 to 32 kb/s, or Opus at 64 to 96 kb/s.
To keep everything: FLAC, or ALAC for Apple devices. Both are lossless and about half the size of WAV.
For audio editors and DJ software that want plain PCM: WAV or AIFF.

Converting a lossy file (MP3, AAC, Opus, Vorbis) to a lossless format keeps it exactly as it sounds now, but cannot restore what the lossy encoder removed. Converting lossy to lossy costs a little quality each time, so keep the bitrate at or above the source’s.

Does anything get uploaded?

No. Your files are read, measured and converted on your own device, and the results are handed straight back to your browser. andu.ro never receives it, so there is no size limit beyond your device’s memory, and an hour-long DJ mix converts as easily as a single track.

How it works

The converter runs FFmpeg compiled to WebAssembly (ffmpeg.wasm) in a background thread, for reading every format and for writing all of them except AAC. AAC and HE-AAC come from the Fraunhofer FDK AAC encoder, also as WebAssembly, fed directly from FFmpeg’s decoder so even long files never sit in memory as raw audio. The waveform and the audio check are measured from that same decoded stream. M4A files are written with explicit HE-AAC signalling and gapless playback info, so players report the real profile and sample rate.

The engine is a 10 MB download the first time you open a file, then your browser keeps it. It needs a browser from 2023 or later, on a computer or a phone.