Yes, HappyMod is safe. HappyMod is a marketplace or a collection of various mod APKs which are provided for the customers free of cost. It has a collection of thousands of Mod applications and games which can be safely used by customers. For any mod apps to get uploaded and listed on HappyMod, they will have to go through a strict virus check, according to the creators. So, it is mostly safe to download mod apps from HappyMod. It is just a tool or platform which helps you to download your required mod applications.  But just like in the google play store, chances are still there for malware or trojans to be hidden in any of the mod apps available on the platform. So, it is extremely important to run your downloaded app through a virus scan before pursuing the installation. The number of google reviews and Quora reviews majorly identifies HappyMod as a safe place that meets your mod apps requirements. The only thing that you need to be aware of is that being a free platform, HappyMod has such a wide collection of mod apps, and there will always be a risk associated when you download an unknown app, and thus, make it a habit to check the downloaded app with an appropriate virus scanner before installing it.