Poly is described as 'Google Poly is a growing archive of Creative Commons licensed 3D models to make it super easy for developers to find viable characters, icons and other models for use in their AR and VR projects and also for artists, photographers and modelers to showcase their creations' and is an website in the Photos & Graphics category. There are three alternatives to Poly, not only websites but also apps for SaaS, Unity, Java and Node.JS. The best alternative is Sketchfab, which is free. Other great sites and apps similar to Poly are SketchUp 3D Warehouse (Free) and echoAR (Free Personal).
Sketchfab is the first web service to publish interactive 3D content online in real-time without plugins. Every new format has its global platform: videos have Youtube, photos have flickr, sounds have Soundcloud... Now 3D files have Sketchfab.
echoAR is a cloud platform for augmented and virtual reality (AR/VR) that provides tools and server-side infrastructure to help developers & companies quickly build and deploy AR/VR/3D apps and content.