S3 storage costs $0.03 per GB and gets cheaper the more is stored, PUT, COPY, POST, or LIST requests are $0.005 per 1,000 requests and GET and all other requests are $0.004 per 10,000 requests. And with some restrictions is available for free for a year.
Amazon S3's web interface is quite confusing, especially for first-time users, but there are many tutorials online that help beginners to set up a static site on S3.
To set up a custom domain, Amazon Route 53 has to be configured as the DNS provider with the domain registrar, two buckets have to be created and configured with the name the same as the domain - one including, one excluding www. A more in-depth explanation can be found here.
A custom domain can be added by creating a CNAME file with the necessary domain in the root of the repository and adding/changing corresponding DNS entries.
One of GitHub's features is a very powerful web editor which helps users edit or even create files right from the web browser, once the file is saved it's the same as a commit. Coupled with pages, this tool becomes even more powerful, giving users a free CMS that is easy to use and create.
A simple, blog-aware static site generator, Jekyll makes it easy to create site-wide headers and footers without having to copy them across every page. It also offers some other advanced templating features.
Due to GitHub's DDoS mitigation technology, users who host their static websites on their servers, cannot have a custom root domain. For example: "example.com" cannot be used, "www.example.com" must be used instead. While in theory the first one is allowed, it greatly affects loading times.
Low cache expires - GitHub sets the cache-control: max-age header to 600 seconds, or ten minutes. Normally, you would set this value to a year so that it stays cached, and then use fingerprinting on your assets. Instead of serving style.css, you would serve something like style-62c887ea7cf54e743ecf3ce6c62a4ed6.css. As it stands now, assets are rarely going to be cached on repeat visits.
This will give a low score on https://developers.google.com/speed/pagespeed/insights with a 'should fix' recommendation around 'Leverage browser caching'.
For a high traffic site this may have implications
The configuration is very simple and preconfigured for most static sites generators/frameworks. You fill 4 fields, you wait 2 minutes and your app is deployed.
The integration with GitHub gives you a deploy preview for all branches and Pull Requests. It sends notifications to GitHub with deploy URL. Very useful for reviewers.
Google acquired Firebase in Oct. 2014. This gives Firebase a degree of trustworthiness in their service and future support since they are backed by such a large company
The content is deployed immediately through the Firebase CLI. Once it's uploaded, the content is served immediately. If you have made a mistake, you don't need to re-upload a new version, through the Admin dashboard you can easily rollback to a previous version.