How are stickers made to stick (WhatsApp, Facebook or Anywhere else)

[jtv1]

I thought I would take a risk and install a range of these 'stickers' but found that they don't have access to the application their for or any other application.
I have given them the liberty to run, but their not taking it!

 

[SpookDroid]

Stickers for these apps are only supported from their own sticker 'stores', not from external sources. If you use a 3rd party keyboard that supports stickers, you might see those but depends on the app you're using if image attachments are supported (these wouldn't be inserted as stickers but as images/GIFs/Video attachments). I would refrain from using any app that claims to install stickers for these and give them full access to your phone...