If you have a video file in MP4 format and you want to extract the audio track and save it as an MP3 file, you can use one of the many online converters that are available for free. Here are some of the best ones that you can try:

• Convertio: This is a popular and easy-to-use online tool that can convert MP4 to MP3 in a few clicks. You can upload your files from your computer, Google Drive, Dropbox, or a URL. You can also adjust the bitrate, audio channels, and other settings before converting. The converted files can be downloaded or saved to your cloud storage. Convertio supports more than 200 formats and has a high quality rating .
• FreeConvert: This is another online converter that can convert MP4 to MP3 with high quality. You can upload your files from your computer or a URL. You can also batch convert multiple files at once. FreeConvert has a simple interface and a fast conversion speed.

To use these online converters, you just need to follow these steps:

1. Upload your MP4 file(s) by clicking the “Choose Files” button or dragging and dropping them on the page.
2. Select “MP3” as the output format.
3. Click the “Convert” button and wait for the process to finish.
4. Download your MP3 file(s) by clicking the “Download” button or saving them to your cloud storage.

That’s it! You have successfully converted your MP4 video to an MP3 audio file online for free.

There are some advantages and disadvantages of using online converters to convert MP4 to MP3. Here are some of them:

• Online converters are free and easy to use. You don’t need to download or install any software on your device.
• Online converters can work on any device and any browser. You can access them from anywhere and anytime.
• Online converters can support a wide range of formats and settings. You can choose the output quality and parameters according to your needs.

• Online converters may have some limitations on the file size, number, and duration. You may not be able to convert large or long videos online.
• Online converters may have some security and privacy risks. Your files may be stored on a third-party server or accessed by others without your permission.
• Online converters may have some quality loss or errors during the conversion. Your files may not be converted accurately or completely online.

Therefore, you should consider these factors before using online converters to convert MP4 to MP3. If you want more control and security over your files, you may want to use a desktop software or an app instead.

If you prefer to use a desktop software or an app to convert MP4 to MP3, you can find many options online. Here are some of the best ones that you can try:

• VLC Media Player: This is a free and open-source media player that can play and convert almost any video and audio format. You can use it to convert MP4 to MP3 by following these steps:
1. Open VLC and click on “Media” and then “Convert/Save”.
2. Add your MP4 file(s) by clicking on “Add” or dragging and dropping them on the window.
3. Click on “Convert/Save” and select “Audio – MP3” as the profile.
4. Choose a destination folder and a file name for your MP3 file(s).
5. Click on “Start” and wait for the conversion to finish.
• Freemake Video Converter: This is a free and powerful video converter that can convert MP4 to MP3 and many other formats. You can use it to convert MP4 to MP3 by following these steps:
1. Download and install Freemake Video Converter from its official website.
2. Launch the program and click on “+Video” to add your MP4 file(s).
3. Click on “to MP3” at the bottom of the window.
4. Choose a preset or customize the output settings according to your preferences.
5. Click on “Convert” and choose a destination folder for your MP3 file(s).
• Audacity: This is a free and open-source audio editor that can record and edit audio files. You can use it to convert MP4 to MP3 by following these steps:
1. Download and install Audacity from its official website. You may also need to install the LAME MP3 encoder separately.
2. Launch Audacity and click on “File” and then “Open”. Select your MP4 file(s) and click on “Open”.
3. Click on “File” and then “Export”. Choose “MP3 Files” as the format.
4. Enter the metadata and adjust the quality settings as desired.
5. Click on “Save” and choose a destination folder for your MP3 file(s).

These are some of the best desktop software or apps that can convert MP4 to MP3 with high quality and speed. You can choose the one that suits your needs and preferences best.