This new release of Debian again comes with a lot more software than its predecessor jessie; the distribution includes over 15346 new packages, for a total of over 51687 packages. Most of the software in the distribution has been updated: over 29859 software packages (this is 57% of all packages in jessie). Also, a significant number of packages (over 6739, 13% of the packages in jessie) have for various reasons been removed from the distribution. SOURCE: debian.org
FROM JESSIE
deb http://httpredir.debian.org/debian jessie main
deb http://httpredir.debian.org/debian jessie-updates main
deb http://security.debian.org jessie/updates main
TO STRETCH
deb http://httpredir.debian.org/debian stretch main
deb http://httpredir.debian.org/debian stretch-updates main
deb http://security.debian.org stretch/updates main