I have to add GTM and Firebase code in all the pages.

[mayank2108]

I haved added the code in my _app.js useeffect method. But due to this lighhouse is showing unused javascript code. What should be the proper placement for the initialization of these 2?

[jamesmosier]

Hi @mayank2108, this answer sounds like it would be useful: #13682 (comment)

A quote from that answer that may answer your question is:

It is somewhat inevitable that some subset of JavaScript will be unused when using someone's library.