[vaduz]

To add to this, in the US, registering is also necessary to sue for infringement (since the 2019 Fourth Estate ruling in SCOTUS) and it determines if the statutory damages apply or not - registration must come before infringement. It's not at all required to file a takedown notice, though.

[devrand]

My understanding is that registration is not required before infringement occurs, but it is required before a copyright lawsuit can proceed. That is, any lawsuits with regard to a unregistered copyright will be paused until the copyright is registered.

[vaduz]

The lawsuits regarding unregistered copyright are and were expressly forbidden under Copyright Act of 1976 - 17 U.S.C. 411 [0] (with the specific exception for the case where all procedures were met, but registrations has been refused), but some districts used to consider the mere filing of the papers as sufficient to sue under, and some did not. SCOTUS resolved it in the Fourth Estate case by reaffirming that you are required to hold a registration of the work to sue for copyright infrigement of that work. [1]

THe "infringement before registration" does not affect the ability to sue for it - it only affects the ability to get statutory damages [2], which is where the huge figures are coming in, as you do not have to prove actual damage - but it does mean that any lawsuits filed before registration is obtained are to be dismissed due to lack of standing and of course statute of limitations also applies.

There are some othe exceptions but they consider unpublished works and/or works within 3 months from publication, so they don't often come into play.

[0] https://www.govinfo.gov/content/pkg/USCODE-2010-title17/html...

[1] https://supreme.justia.com/cases/federal/us/586/17-571/

[2] https://www.govinfo.gov/content/pkg/USCODE-2010-title17/html...