Free online PART to MP3 converter

A phone, car stereo, audio editor, or sharing platform may require a finished .mp3 file after an Internet download has been interrupted and left as .part. The download must be completed first because conversion cannot reconstruct audio data that never arrived.

What the PART format is

.part is a temporary filename suffix used by browsers and download managers while receiving a file. Mozilla Firefox and some download managers may create names such as recording.mp3.part; Chromium-based browsers commonly use .crdownload instead.

PART does not identify an audio codec or container. The underlying download may be an MP3, WAV, FLAC, video, archive, document, or another file type. A paused, failed, or crashed download may retain the temporary file so the original program can resume it. Its filename and current size do not prove that the data is complete.

What the MP3 format is

MP3 is a lossy, compressed audio format supported by phones, computers, car stereos, media players, and most audio editors. It reduces file size by discarding audio information judged less audible, making it practical for playback, sharing, and portable storage.

Typical export settings range from 128–192 kbps for smaller files to 256–320 kbps for higher-quality output. MP3 is not an ideal editing master because encoding an already lossy source again can add artifacts and cannot restore discarded detail.

How to convert a completed download

1. Resume or restart the download. Use the browser or download manager that created the PART file. In Firefox, open Menu → Downloads and resume the relevant transfer. When the transfer succeeds, the program normally removes .part and restores the original filename.
2. Keep a copy before manual testing. If the source is unavailable but the program reported completion, copy the file and remove only .part from the copy when the intended original extension is known. For example, recording.mp3.part can become recording.mp3. Renaming changes only the filename; it does not convert or repair the data.
3. Identify the actual file type. FFmpeg's inspection utility can examine a file without relying on its suffix:

ffprobe -v error -show_format -show_streams "downloaded-file.part"

If the output shows a complete audio stream, convert it with FFmpeg:

ffmpeg -i "downloaded-file.part" -map_metadata 0 -vn -codec:a libmp3lame -q:a 2 "output.mp3"

-q:a 2 requests variable-bitrate MP3 output at roughly 190 kbps. Use a fixed bitrate when a device or workflow requires one:

ffmpeg -i "downloaded-file.part" -map_metadata 0 -vn -codec:a libmp3lame -b:a 192k "output.mp3"

If inspection confirms that the completed file is already MP3, do not re-encode it. Remove .part from a copy or copy the data to an .mp3 filename instead.

For a graphical desktop workflow, open the completed audio in Audacity and choose File → Export Audio, select MP3, and set the bitrate. Audacity may require FFmpeg support for some input formats, and exporting an MP3 source as MP3 causes another lossy encode.

You can also upload a completed, recognized audio file to the free converter on 101convert.com without installing software. Uploading an unfinished PART file cannot recover missing data.

Quality and compatibility limits

Convert from the original completed WAV, FLAC, or other lossless source when available. Converting from an existing MP3 or another lossy format preserves its existing losses and may add more. MP3 export can also omit or change metadata, cover art, chapters, and additional audio streams.

FFmpeg may read a partially downloaded file and create a truncated MP3, but the result can end abruptly, contain decoding errors, or omit metadata; this is not a repair. If ffprobe finds no usable audio stream, obtain the download again rather than repeatedly renaming or converting it. A PART file containing video, an archive, or another non-audio format cannot become MP3 by changing its extension.