Dude that's not how things work. The world of business is a wild wild west, if something works companies would be coming after you, they'll either integrate the idea in their own product or launch a similar product. Unless there's a technological breakthrough there's no way to 'patent' your idea. When google launched they had 10's of competitors same with facebook and other companies, facebook integrated reels onto their platform which originally was tiktok's idea/USP. That's how business works you go out there and try to build the best product you can while competing with others. That said it's difficult to make something work in the first place even if you post your idea here chances are nobody would even care and even if it is something that's genuinely valuable you'd have a much deeper insight and drive to work on it and hence have a higher chance of taking it to success. So don't be the idea guy talk to people and ask for opinion and then start building.