If you do your due diligence when installing or updating dependencies, you've probably gone to a project's GitHub to have a look at its source code. However, there's no guarantee that the code on GitHub is what was actually published to npm.
xray.computer lets you read the exact code you'll be running when you install or update a package. This type of manual review is one of the tools in our arsenal when it comes to catching supply chain attacks like the one in event-stream.
This project borrows very heavily from Hex Preview and Hex Diff. It's not quite a fork, but it's not too far from it. Both of these tools are great parts of the Elixir ecosystem; xray.computer is an attempt to bring the same capability to other package registries.