Turn WAV, M4A, OGG, FLAC or MP3 into MP3 or WAV. Pick the bitrate. Files stay on your device.
This tool converts an audio file to MP3 or WAV by decoding it with your browser's own audio decoder and then writing the new file on your device. The browser turns the file into raw samples, the numbers that describe the sound wave. For WAV, those samples are written out as 16-bit PCM, the plain uncompressed format. For MP3, they go to the LAME encoder, compiled to WebAssembly, which compresses them. That means the tool can only read what your browser can play. MP3, WAV, M4A and AAC, OGG and FLAC work in current Chrome, Edge and Firefox. Safari plays MP3, WAV, M4A and FLAC but has been slower to support OGG, so an OGG file may be refused there with a clear message.
Constant bitrate (CBR) gives every second the same number of bits, so the size is predictable: seconds times kilobits per second times 1000, divided by 8. A 3-minute song is 180 seconds, and at 192 kbps that is 180 times 192,000 divided by 8, which is about 4,320,000 bytes. That is 4.32 MB counting a million bytes to the MB, and 4.1 MB in this tool's size lines, which count 1 MB as 1024 KB. At 128 kbps the same song is about 2,880,000 bytes, and at 320 kbps about 7,200,000. These are estimates of the audio data: the real file is a little larger because of frame headers and padding (in a test run, 2,880,574 bytes at 128 kbps). Variable quality lets the encoder spend more bits on busy passages and fewer on quiet ones, so the size is not known in advance; V0 is the best and V6 the smallest here. Mono merges the left and right sound into one channel. At a constant bitrate the file size stays the same and all the bits go to that one channel, so choose a lower bitrate for mono speech; with variable quality a mono file comes out smaller. The sample rate is Automatic unless you pick 44.1 or 48 kHz: the file's own rate is used when MP3 supports it, 96 kHz becomes 48 kHz, and a bitrate over 160 kbps lifts a rate under 32 kHz to 44.1 kHz. The result line shows the rate that was written.
A WAV file holds 44,100 samples per second per channel at 2 bytes each, so one minute of stereo at 44.1 kHz is 60 times 44,100 times 4 plus a 44-byte header, which is 10,584,044 bytes, a little over 10 MB. A 3-minute stereo WAV is 31,752,044 bytes, about 30.3 MB, against 4.1 MB for the MP3 at 192 kbps. Converting an MP3 or M4A to WAV does not bring back detail that the first compression threw away; the file just becomes bigger. Converting a lossy file to MP3 again adds a second round of loss, so keep the original if it matters. Going from WAV or FLAC to MP3 is the case where the conversion makes sense, because those start with every detail.
Each file is read and decoded fully in memory, so a file may be up to 100 MB. The decoded sound must also fit a memory budget, which depends on its length, sample rate and channels: about 11 minutes of 48 kHz stereo on a computer, about 5 on a phone or tablet, and up to 30 minutes of mono at lower rates. Longer sounds are refused with a message. The browser must decode the whole file before this can be checked, so a very long compressed file can still run out of memory. Up to 20 files can be added at once, one at a time. Files with more than two channels keep only the front left and right. Tags such as title, artist and cover art are not copied, because the sound is rewritten from samples. The page loads the MP3 encoder, about 0.9 MB (its script and its WebAssembly file), only when you first convert to MP3. The audio is processed in this tab and a background worker; it is not sent to a server. The encoder is LAME, which is licensed under the LGPL, and the page links to the LAME project.
Add the WAV file, leave Convert to on MP3, pick a bitrate such as 192 kbps, and press Convert. A 3-minute stereo WAV of about 30 MB comes out near 4.1 MB at 192 kbps. The conversion runs in this tab, so nothing is uploaded.
128 kbps is a common size for spoken audio and casual listening, 192 kbps is a step up, and 256 or 320 kbps leave the most detail. Each step up grows the file: a 3-minute song is 2.7 MB at 128 kbps and 6.9 MB at 320 kbps. Compare by ear on your own file.
The tool uses your browser's own decoder, so it only opens formats the browser can play. An OGG or Opus file may fail in Safari, and a damaged file or one without an audio track fails everywhere. Try Chrome, Edge or Firefox, or convert the file to WAV with other software first.
Yes, a little. M4A with AAC is already compressed, and MP3 compresses the decoded sound a second time. At 192 kbps or more the extra loss is small for most listening, but it cannot be undone. The original M4A is unchanged, so keep it.
WAV stores every sample, 2 bytes each, so stereo at 44.1 kHz is about 10 MB per minute. An MP3 at 192 kbps is about 1.4 MB per minute. WAV is the choice for editing or burning a disc; MP3 is for sharing and storage.
No. The file is decoded and encoded in your browser, in this tab and a background worker, so no server receives your audio. The page counts visits with Google Analytics using rough groups such as 1 to 10 MB, never a file name or a sound. Your format and MP3 settings are remembered on this device.