Note, entries marked by an * were backported to 1.9 as well. Here are all the changes that were made since 1.9 was set as the stable branch:

Improved methodmap API and documentation.

Lots of stability and code quality improvements.

Adjusted plugin binary format to pave the way for more advanced language features.

Faster compile times due to numerous fixes and tweaks.

A new command to reload the databases.cfg without restarting the server: sm_reload_databases.

Updated MySQL client library for utf8mb4 charset support.

New trace ray natives to query for more infos along the ray.

Support for running on 64-bit dedicated servers.

The new version includes community contributions by the following awesome people: headline, SlidyBat, PerfectLaugh, quasemago, Technoblazed, InvexByte, TiBarification, Pelipoika, Peace-Maker, thewavelength, rumblefrog, jason-e, Kailo, CrazyHackGUT, rsKliPPy, fakuivan, maximsmol, Silenci0, hydrogen-mvm, Hexer10, ddhoward, Bara, PowerLord, TheByKotik, komashchenko, BotoX, b3none, DJPlaya, PerfectLaugh, 404UNFca, JoinedSenses, TheDS1337, Batfoxkid, MartLegion, FortyTwoFortyTwo, PlayBo圓1, and Einyux. As always, there will be gamedata updates for the old-stable 1.9 branch for a while. The new stable branch of SourceMod is now 1.10.

Mods for cs go