What are Skynet Portals?
Portals power Skynet. A Skynet portal is a low cost server that sits between Skynet and everyday users, enabling them to access Skynet content without needing to operate any special software themselves.
There are standard Skynet portals, which is a regular Sia node configured to be a portal. These are typically used privately by the individuals who set them up.
Then there are Skynet webportals, which has a web UI built on top of it, and is publicly accessible using your browser. Since webportals pay their own bills and for the files uploaded to them, they will likely have their own policies on how many and what types of files you can upload.
Here is a list of Skynet webportals available at launch:
https://siasky.net/ - an official portal from Nebulous
https://sialoop.net/ - by Hakkane, of keops.cc
https://skynet.luxor.tech/ - by Luxor, a longtime partner
https://skynet.tutemwesi.com/ - by Tutemwesi, a trusted community member
https://siacdn.com/ - by ericflo, a trusted community member
https://vault.lightspeedhosting.com/ - by Lightspeed Hosting, a cloud and colocation data center
https://skydrain.net - by Fornax, who has been making apps on Sia since near the beginning
https://skynethub.io/ - by Crypto-Rocket, a trusted community member
Any Skynet file can be retrieved by any Skynet portal. Additionally, anyone can run a Skynet portal - a Skynet portal is essentially a normal Sia node that forms contracts with every host instead of just a handful of hosts. As of writing, this costs about $10 per month in blockchain transaction fees.
Skynet portals are fully interchangeable, a fact which is key to the decentralization of the network. If one portal goes offline or begins ratelimiting or overcharging, a new portal can easily take the place of the old one.
You can find everything you need to set up and run your own Skynet webportal here.