Need help for Youtube MP4 conversion from my Windows 11 PC

BigConv Firefox addon.

It is a free Firefox extension that lets you convert the video clips to either MP3 or MP4 format in high quality directly from youtube. It's a lightweight, beginner-friendly tool that eliminates the need any 3rd-party websites.  The download and conversion is triggered with just a single click while you're already watching a video on YouTube.

Step 1: Go to the BigConv Firefox Add-on page and click Add to Firefox to install the extension.

Step 2: Open YouTube in Firefox and navigate to the video you want to convert.

Step 3: Click the BigConv toolbar icon while watching the video — a compact popup will appear, offering options to convert to either MP3 or MP4. 

Step 4: Click your desired format and a new tab will open on the BigConv website, initiating the conversion process automatically.

Step 5: Select your preferred format and start the conversion by clicking the corresponding button. Once complete, download the file by pressing the Download button. 

For me, BigConv is a convenient one-click free youtube mp4 converter without leaving your browser. It's free, easy to use, and requires no technical knowledge. However, it currently holds a 2.6 out of 5 rating from users, so it may not be the most reliable option for everyone — it's worth trying but have a backup tool in mind just in case