: Best for finding royalty-free stock footage and square motion backgrounds in 4K or HD that can serve as the base for an intro.

: Offers a massive library of customizable square video templates. You can edit them directly in your browser and download the final result as a high-resolution MP4 file .

Canva. Website's a PITA, but you can produce some good looking material using it. Free Intro Maker: Create YouTube Video Intros - Canva

: Dynamic 3D or flat animations that gather particles or lines to form your brand logo.

: Clean designs using simple typography and subtle transitions for a professional business look. How to Download and Use MP4 Templates

: A popular choice for mobile and web creators, offering a wide range of free intro templates (cinematic, gaming, etc.) that can be exported in compatible formats for social media.

: Provides free, ready-to-use square templates specifically for Premiere Pro and After Effects . These often include title sequences and animated borders framed for square formats.