I need my session ID for a secret server plugin I'm making. I need my session ID to test it. How can I manually get a session ID? Can I do it in-game? Do I have to crash it to find my session ID? If I crash it does my session ID change? Just for those of you who would like to know, if I have to crash it I can't get F3 + c to crash my game. I'm on a Mac, is the crash command different? If someone could answer all these questions I will be amazed.
52 Answers
Session ID
The Session ID can be found in your game log/crash report before the 1.9.1.
Version
In/After 1.9.1-pre3, the session ID has been removed from the game log/crash report. 
Here is how the crash report looks like before 1.9.1 and after 1.9.1:
This is 1.9 crash report
This is 1.9.2 crash report.
As a result, you can only view your session ID before 1.9.1.
Game Log
The Session ID can not only be found on crash report, it can also be found on the game log. (Before 1.9.1) 
Does my session ID changes if I logout?
Yes
1st game log
After reopen Minecraft
How to check session id without crashing the game?
Just go to your .minecraft folder and you will see a folder called logs
Make sure Minecraft is launched. If it isn't, you will see the old session ID. Inside the logs folder, you will see a text document called latest, open up latest and you should see your session ID.
Extra
Currently, there is no way to view your session ID in-game
Hold F3 + C for 10 seconds to crash the game.
Thats' it, I hope it helped :)
2You can press F3 + C for 10 seconds crash the game and get your session ID.
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