I found myself repeatedly copying and pasting individual keys and values from .env files when deploying applications and became frustrated with this.
I like the experience of using Vercel, where you can copy an entire .env file this tool to seperate keys and values from .env file and let me copy them easily is a way for me slightly improve my experience until the platforms I use implement a similar feature.
Yes, it is unsafe. I made this site for my personal use and while I use this even with my sensitive information, I wouldn't recommend others to do so. But since this is just a HTML file with a bit of JavaScript, you can see the code yourself and run it locally if you want to.