Audio Converter Online: WAV, Opus and AAC from Many Files

How to use it

Choose one or more audio files in the box above.
Set the Output format, Sample rate and Channels.
Press Convert files, then download each file, or Download all as ZIP when there are several.

What each output is

WAV is uncompressed PCM audio and the largest of the outputs. 16 bits per sample is the usual depth for delivery, and 24 bits leaves more room for editing. Opus and AAC are compressed, so they make much smaller files for speech and music. Opus is written in an Ogg file (.opus) at 48 kHz; AAC-LC is written as a raw ADTS stream (.aac), which most players open directly.

Sample rate and channels

The sample rate is changed by the browser's own resampler, so the sound is resampled rather than relabelled. Stereo is mixed to mono by averaging the two channels, and mono is copied to both channels when stereo is chosen. Files with more than two channels are mixed down to stereo for Opus and AAC.

Why MP3 is not offered

Browsers have no built-in MP3 encoder, and the open MP3 encoders, such as LAME, are licensed under the LGPL, which this site does not bundle. Opus and AAC give much smaller files than WAV and are widely supported, so they cover most needs without an MP3 encoder.

Example: one second of stereo audio

One second of stereo audio at 44 100 Hz in 16-bit WAV is 44 100 frames × 2 channels × 2 bytes = 176 400 bytes of samples, plus the 44-byte header: 176 444 bytes.

Frequently asked questions

Why is MP3 not in the list?

Browsers cannot write MP3 files, and the open MP3 encoders are under the LGPL licence, which this site does not include. WAV is the most widely supported output; Opus and AAC give smaller files.

Are my files uploaded?

No. Each file is decoded, converted and encoded in your browser. Nothing is sent to our server, and the results stay on your device until you download them.

Why does Opus ignore the sample rate I choose?

Opus is written at 48 kHz, the rate its encoder works at, so the sample rate choice does not apply to it. Choose WAV or AAC if you need a different rate.

Why does the page say my browser cannot encode AAC or Opus?

Encoding these formats needs the browser's audio encoder, which not every browser provides. Use WAV, which every browser can write, or try a current version of Chrome or Edge.

Which output should I choose?

WAV for editing and the widest support, Opus for small files of speech or music, and AAC for files that devices and players expect in that format.

How large a file can I convert?

Each file can be up to 150 MB, and you can convert up to 20 files at once. A large file in a high-quality format needs much of the browser's memory while it is converted.

Sources

Figures and text last checked on Tuesday, November 10, 2026.