Free online MP3 to MP3 converter

A program or device may require a newly encoded MP3 with a particular bitrate, sample rate, channel mode, or metadata layout. Re-encoding can also reduce file size, but copying an MP3 without changing its encoded audio is not format conversion.

What the MP3 format is

MP3, formally MPEG-1 or MPEG-2 Audio Layer III, is a lossy compressed audio format. Its perceptual encoder removes audio information expected to be less audible, producing much smaller files than uncompressed PCM audio such as WAV.

MP3 files are encoded by software such as LAME, FFmpeg, Audacity, iTunes, Apple Music, Windows Media Player, and digital audio workstations. The format is common in music libraries, podcasts, voice recordings, downloads, portable players, car stereos, media players, and services that accept standard audio uploads.

What the MP3 format is good for

MP3 is suitable when small files and broad playback compatibility matter more than retaining every detail of the original recording. Operating systems, phones, web browsers, editing applications, and consumer audio equipment generally decode it without additional software.

Typical settings include 64–96 kbps mono for speech, 128–192 kbps for many general-purpose files, and 256–320 kbps for higher-quality music. Constant bitrate (CBR) gives predictable file sizes and compatibility; variable bitrate (VBR) usually gives better quality at a similar average size. MP3 supports mono, stereo, common sample rates such as 44.1 and 48 kHz, and metadata commonly stored in ID3 tags, including title, artist, album, and cover art.

How to convert one MP3 into another

Since both files use the same format, conversion normally means decoding the source and encoding a new MP3 with different settings. Keep the source and destination names different so the original is not overwritten.

FFmpeg provides precise control from the command line:

1. Install FFmpeg and place input.mp3 in the working directory.
2. For constant 192 kbps output, run ffmpeg -i input.mp3 -c:a libmp3lame -b:a 192k output.mp3.
3. For LAME VBR output, run ffmpeg -i input.mp3 -c:a libmp3lame -q:a 2 output.mp3. With the LAME encoder, lower quality values produce higher quality; -q:a 2 is a common high-quality music setting.
4. To resample to 44.1 kHz and force stereo, run ffmpeg -i input.mp3 -ar 44100 -ac 2 -c:a libmp3lame -b:a 192k output.mp3.

In Audacity, choose File → Import → Audio, open the source, then choose File → Export Audio. Select MP3, set the bitrate mode and quality, provide a new filename, and export. Audacity can also edit the exported file's metadata.

For conversion without installing software, upload the file to 101convert.com, select MP3 as the output, choose the available audio settings, and download the result. 

If the encoded audio must remain unchanged and only another file copy is needed, use ffmpeg -i input.mp3 -c:a copy copy.mp3. This avoids decoding and re-encoding, so it does not change the audio bitrate, sample rate, channels, or quality; it may only rewrite the MP3 file structure or metadata.

Quality and compatibility limits

Every lossy re-encode can discard additional information. It cannot restore detail removed by the original encoding, and encoding an MP3 again at the same or a lower bitrate can increase swishing, pre-echo, and high-frequency smearing. Preserve the original MP3, or preferably the lossless source, and create new versions from that source whenever possible.

Lowering the bitrate reduces file size but also reduces audio quality. Changing 44.1 kHz to 48 kHz does not improve an existing recording and can introduce resampling artifacts. Use mono for speech when stereo is unnecessary; use CBR when an older device has trouble with VBR.

Check the result with ffprobe output.mp3 or a media player's file-information panel. Verify the bitrate, sample rate, channel count, duration, and tags. Older hardware may reject unusual sample rates, very high bitrates, VBR files, or oversized ID3 artwork; CBR 128–192 kbps stereo with conventional ID3 tags is generally a conservative compatibility choice.