What is now accepted to backup?

Question

Backup

Hello.
Suddenly I decided to take care of the issue of backup.
In light of the fact that the last time I was interested in this for a long time, I remembered only DVD.
Useful to google. Found 25/50GB Blu-Ray discs/drives. It seems to be for 100, but it's not very clear whether they are sold (I didn't find it right away).
Actually the question is: does it make sense to buy a Blu-Ray drive, or is there some more recent technology that I have not noticed?
Well, if there are "definitely good" manufacturers, their names would not hurt.
Backing up a HDD of several terabytes to smaller (50GB) volumes of discs is somewhat difficult;)