How to Change Forum URL
If you want to change phpBB forum URL which is being used to access the forum, the process is quite simple and easy. All you have to do is to change domain name in phpBB server configuration.
First, login to phpBB administrator control panel and find “SERVER CONFIGURATION” to access cookie and server settings.
To change cookie domain name, click on “Cookie settings”. It will open phpBB cookie settings.
There you can change the current domain name. To do this, replace it in the “Cookie domain” value. Apply the changes by clicking on “Submit” button.
Next step is to change domain name in the “Server settings” which is located in the same menu as “Cookie Settings”.Find a field for “Domain name” and change existing domain name with new one.
To apply the changes, click on “Submit” button. Finally, clear the cache and try to open the forum by using new URL. It should be working with the new URL after the changes.