Download Audio from YouTube: Convert MP4 to MP3 [Python + Pytube + FFmpeg]

Download audio from any YouTube video of your choice and convert to MP3 format.

Harsha Nanayakkara
4 min readOct 4, 2022


UPDATE: The Initial code has been updated to set a customized location — instead downloading the file to the same location where code resides — for the downloaded audio file. Therefore, the article also has been updated using the UPDATE keyword where necessary.

I usually like to download music or songs from YouTube, just the audio. However, I saw that many online downloaders download the audio in MP4 format. Conversely, I prefer all my audio files to be in MP3 format. Therefore, I thought to write a program that will help me to download and convert the audio files at once.

This code covers the below use-cases;

  • This code is written on Windows machine so some steps may differ for other operating systems.
  • Asks for user input to get the YouTube video URL.
  • Initially, downloads the highest bit-rate audio stream in mp4.
  • UPDATE: Custom path can be set as the download location.
  • Rename the downloaded file name.
  • Convert the file to mp3.
  • Delete the initially downloaded mp4 file after conversion.


Now, let’s dive into the code.

First of all we need to import the required libraries.

from pytube import YouTube
import os

UPDATE: Path variable added to customize the download location. For example, the following line will set the download path as D:\Music\Mix\ .

path = 'D:\Music\Mix\\'

Then, we have to let the user to enter the YouTube URL and save it in video_url variable. After that, YouTube object is created named yt .

video_url = input("Please enter the video URL: ")
yt = YouTube(video_url)

Now, using the YouTube object we can get the highest bit-rate audio stream from the available codecs (defaults to mp4). Once it is selected, the file can be downloaded using the download() method.

UPDATE: Further, customized download path has been set using the output_path parameter.

audio = yt.streams.get_audio_only()

Now the mp4 audio file should have been downloaded. Next, it is required to start the conversion. For that, we need the downloaded file name with extension.

file_name = audio.default_filename

UPDATE: Path and file name needs to be taken as an input for the next step, which is to rename the file to exclude any white spaces.

source = path + file_name

I have used FFmpeg to do the conversion. Therefore, for the program to work correctly no white spaces are allowed in the file name. So, I have replaced white spaces with underscore (_).

if ' ' in file_name:
os.rename(source, source.replace(' ', '_'))
file_name = source.replace(' ','_')

os.rename replaces the white spaces with underscore in the downloaded mp4 file. source.replace will do the same thing but, will assign the new name to file_name variable for us to use later.

Up to now we have file name with mp4 extension. We also need to set the output file with mp3 format. For that, I have taken the same name without the extension. os.path.splitext() splits the extension and the rest of the file name. os.path.splitext(file_name)[0] will give us only the file name without the extension part.

file_without_ext = os.path.splitext(file_name)[0]

Now we have all parameters needed for the mp4 to mp3 conversion using FFmpeg.

Note: ffmpeg\bin should be added to the Windows Environment Variable in order to the command to work.

Otherwise, it will give following error

‘ffmpeg’ is not recognized as an internal or external command,
operable program or batch file.

command = f"ffmpeg -i {file_name} {file_without_ext}.mp3"

Finally, we have to instruct the OS to run the above command and clean up the previously downloaded mp4 file.


Great! We have now completed the code. Let’s see how it works.

MP3 download output
MP3 download output

Voila! Happy downloading 😎

Code in GitHub:

I sincerely hope this article will be useful. I highly value your feedback and support!

Thank you for reading and stay safe!



Harsha Nanayakkara

An enthusiastic autodidact who is passionate to gain and freely share knowledge. I would really appreciate your feedback and support!