Our users have written 1 comments and reviews about fdupes, and it has gotten 8 likes
the link point to a old website where the developer say not maintained anymore, last version 1.51 pointing to a dead link ;(
Hopefully a Debian Maintainer decide it was a great softwareso if you look inside you're synaptic you will find the 1.61 version.
apt install -y fdupes
will do the job.