Usage of the TypeScript compiler argument 'skipLibCheck'

To paraphrase the question tersely:

Surely [enabling skipLibCheck] decreases the integrity of the typing of your application?

I would agree that yes, it does. However, if the alternative is an application that does not compile, then it becomes a handy flag.

While Typescript itself is fairly mature, the typescript community is still relatively young. There are type definitions available for tons of libraries, and even some native typescript libraries, but they can be incompatible with one another for a variety of reasons.

You may import a library whose typing is built with a less-strict tsconfig than you would like--which your compiler could complain about when you try to use it.

You could find two libraries define the same types, but incompatibly. I've imported some libraries that supplied their own typings for a Polyfill of Buffer, and my whole application would fail to compile because of their incompatibility.

Enabling --skipLibCheck can help work around these issues. Turning it on will prevent Typescript from type-checking the entire imported libraries. Instead, Typescript will only type-check the code you use against these types. This means that as long as you aren't using the incompatible parts of imported libraries, they'll compile just fine.

tl;dr, Yes, --skipLibCheck degrades type checking, and ideally we wouldn't use it. But not every library provides perfect types yet, so skipping it can be nice.