How to fix 400 error for site visitors on the server side?

Question

Nginx

It turned out that too much data was written in cookies, as a result, some users got 400 errors, how to solve this error? I already wrote in the code to delete such cookies, but the user cannot get to it yet, because immediately upon entering the site it gives a 400 error. Some settings were registered in the nginx configs, but this did not solve the problem. Are there any solutions? Not all users will understand that it is necessary to remove cookies from the browser

Answer 1

1) make JS on the page with deleting the cache and cookies.
2) temporarily put a stub on the main page, in the stub tell how to clear cookies. provide for a transition to the site if the user has already cleaned everything.
3) make an e-mail newsletter for all users of the site.

Answer 2

Why is nginx giving 400? Need log details.