This pull request seems to assume that every user of the library is only using it directly on YouTube's own website and this will blow up for everyone that doesn't (which is probably most users).

A better approach would be to add an extra parameter so the session creation so you can pass the relevant parameters into the library, the same way that visitor data and poToken's are handled.

The changes only apply if the cookie is set, and this only works in the browser not true #707 (comment):
https://github.com/LuanRT/YouTube.js/blob/4942992/src/utils/HTTPClient.ts#L140

Are you suggesting limiting the changes to accepting a data sync ID and setting the X-Goog-PageId header? In that case, the account_index option would need to be removed entirely.

I added a client_name check to make the intent clearer.

Are you suggesting limiting the changes to accepting a data sync ID and setting the X-Goog-PageId header?

Better that it breaking for people passing cookies to YouTube.js on Node, Deno or React Native or people using it in web browsers but not on the YouTube website.

It should be more robust now, the only risks I see are:

• Only the web client will get the X-Goog-AuthUser header, which didn't appear to work previously.
• Other websites will not have additional URL search parameters.

Works with the web client and in Node.js.