MyBB Community Forums

Hello.
My forum now get a bit problem, i don't know how to solve.

At first my forum urls be like:
domain.com/forum/forumdisplay.php?fid=4    ← This URL is now still accessed normally.
Now changed to
domain.com/forum/forum-4.html

And

All threads URLs also changed
domain.com/forum/showthread.php?tid=166    ← This URL is now still accessed normally.
Now changed to
domain.com/forum/thread-166.html

Is this a type of duplicated content or not?
So what is the problem, have you ever been in this situation? And how to solve this issue? 
I want it come back the default URLs to forumdisplay.php?fid=ABC and showthread.php?tid=ABC (ABC: number of id)
Thank you very much.

This is because you enabled search engine friendly URLs if you want to use this please rename the htaccess.txt to .htaccess in your forum root.

To disable it go to

Admin CP -> Configurations -> Server and Optimization Options -> Enable search engine friendly URLs?

Set this to disabled or automatic.

Oh yeah! Thanks Brian. Your answer solved my problems. Thank you so much.
After reading your explaination, i decided to enable Engine friendly URLs.