Firstly, we will discuss the difference between MP4 and mV4 and how to convert an M4V file to MP4. You can look for some compressors and converters, such as Uniconverter, that can help you do every conversion and compression so you save your time. 
M4v :
M4v is a file format introduced by Apple that is similar to MP4. It is used to store video content in the iTunes stores. M4v is only used on Apple devices.
Mp4 :
Whereas MP4 was introduced by the Moving Pictures expert group, which is well known as (MPEG ). Mp4 is a video container format that stores audio, video, subtitles, images, etc.
Compared to M4v, MP4 is commonly used or supported by many mobile devices and online streaming services.
Now, we have to know how to convert m4v to mp4. But before doing so, we must first understand why we must convert our m4v-format video to mp4 format.
There are many reasons to convert M4V format video to MP4. Still, the most common cause is that to avoid compatibility problems, we have to convert our M4V format video to a more device-friendly format.
We can convert our video format by using different converters, which are available online.

Steps to convert m4v to mp4 :
To convert our video format, we must follow the following rules carefully.

1: Install any video converter
Firstly, we have to download any video converter through history to convert a video format.
Then, we have to run the video converter and install that converter by following the guidance that will be seen on the screen.

2: Add the video you want to convert
Secondly, we have to add the video which we want to convert. To add files for conversion, we have to click on the add option, which will appear on our screen.
Then, we have to click on the Add video button. Now, our video, which we have to convert, can be seen on screen, and some people are always confused about whether they can add only one video. Still, as technology is growing, all video converters now have an option that a user can use multiple videos simultaneously. This is very helpful, and now we can save our time.

3: Specify the output file format
The most crucial step in converting video is specifying the output file format using any video converter. First, you click on the video tab to open the video tab, and then you choose the output format. In this case, we are discussing converting m4v to mp4, so we will select the mp4 format as our output version.
If a user wants to convert his or her video format to a particular device, they must click on the devices option.
As we discussed earlier, technology is advancing daily, so detecting everything is straightforward. Even nowadays, mobile devices can easily detect faces, so similar to this, all video converters have this option that we can automatically detect the model of any mobile. To detect automatically, we must plug the device into your computer and click the phone icon.

4: saving your data   
The last step in converting a video format is that all the available video converters save the converted files in a folder by default, which a user can easily change.
If a user wants to change the folder, there is an option to change or create a new folder.
Fin,  Ally, and the last step is to convert the video format from m4v to mp4. All the video converters have the option of "Convert Video.." By clicking on it, our video will start to convert.
After converting, our video will automatically open, and we can quickly transfer it to any other device, such as a Mac or PC.
These are the few steps to easily convert our m4v video format to mp4 video format. Similarly, we can convert mp4 to m4v format.