Some ISPs block Facebook at the DNS level. Changing your DNS to Google (8.8.8.8) or Cloudflare (1.1.1.1) can sometimes bypass simple blocks. However, this method fails against DPI firewalls.
There are several reasons why you might want to use filters on Facebook: filter shekan baraye facebook for android
In countries like Iran, China, Russia, and Belarus, using unauthorized filter breakers is illegal and can lead to fines, imprisonment, or device confiscation. Some ISPs block Facebook at the DNS level