Valve has seemingly been working on some very exciting updates for Steam. One of the developer's patents was recently discovered, and it could, among other things, allow users to play games as they download - similar to what they can do today on consoles (in some cases).
In short, this is a system that allows Steam to track read operations performed by the exe file of a given game, in order to draw a map of what and how often data is being accessed. Valve would then use this telemetry to, for instance, prioritise certain files during the download process to allow players to get started early without having to wait for the whole thing to finish.
The same tech could also help Steam get rid of unused files without compromising the integrity of the game, such as in cases where you need to free up some space. Valve explained that this could even help pre-fetch certain files to reduce latency while loading.
Of course, this type of system is not entirely novel. Playing games as you download them was one of the selling points of the PS4 and Xbox One, and the same tech is in use today by PS5 and Xbox Series X/S.
In fact, Valve itself trialled a version of this all the way back in 2015 at the launch of Mortal Kombat 10, by setting the game to download in smaller chunks. It ended up backfiring, causing a number of problems, and forcing Valve to pull it.
Indeed, even the idea of making certain files independent to reduce a game's footprint is a feature regularly used by Call of Duty, allowing players to selectively download/remove certain components, such as modes, higher-resolution textures and so on while keeping what they want to play.