You can verify this yourself because Burner Note is open source
Burner note came into existing after years of using other products that claim to do
something similar. However their pages are laden with ads, have a poor UI, and you can't know for
sure if they really are actually encrypting / deleting anything.
As a developer I wanted to build something better; something more useable and
technically transparent, and that's what Burner Note is.
The good stuff... Burner Note is open source. Go and check out the code. If you
can't be bothered doing that then I can tell you that from browser to server we are relying on good old
SSL. On the back end we utilise Laravel's out of the box encryption
protocols which are recognised as being both excellent and are also open source.
On clicking the link and opening your note, it is deleted instantly and completely
from our database. Gone forever.