Merging 2 videos simultaneously may seem complex, but it can be done quite simply on CapCut. Let's dive into the process right away!

Merging 2 videos simultaneously with CapCut app
CapCut is a free, professional video editing app available on both iOS and Android. With this app, you can utilize various useful tools to add effects, stickers, adjust video speed, color grading, trim videos, and more.
Additionally, CapCut offers a rather intriguing feature of merging 2 videos simultaneously.
Step 1: Download the CapCut app from AppStore or CH Play.
Step 2: On the app's main interface, tap New Project.

Step 3: Grant CapCut permission to access your photo library.

Step 4: Choose the first video you want to merge >> Add.

Step 5: In the bottom menu, swipe left to open Format >> select 4:3.

Step 6: The 4:3 ratio will transform your video screen into a horizontal rectangle. Adjust your first video to one side of the screen. You can also pinch with 2 fingers to resize the first video.
Then tap the < arrow button to return to the initial toolset.

Step 7: In the initial toolset, select Overlay >> Add Overlay.

Step 8: Add your second video to the app, then adjust it to the remaining side of the screen.

Step 9: To make both videos stop simultaneously, scroll to the end of the timeline, then shorten the duration of the longer video until it matches the shorter one.
Press the < arrow button to return to the initial toolset.

Step 10: Merging 2 videos simultaneously can result in unpleasant audio overlapping. If you're not concerned about the original video's audio, mute them all and replace with a music track.
First, select Mute clip sound, then tap Add sound >> Sound.

Step 11: Press Download (down arrow icon) on the preferred music track, then + to add it to the video.

Step 12: You also need to adjust the music track to fit the video. Once everything is set, hit Export video (up arrow icon). The processed video will be saved in your photo library.

Despite requiring several steps, it's not difficult at all to merge 2 videos simultaneously, right? Share this interesting trick with your friends! Have a great time!