Embedding Youtube videos is very easy under phpBB. When creating a topic or posting a reply, look for the 'Youtube' button under the thread title. Clicking it will insert the following code in to your message:



Now you need the video's code. This is an alphanumerical string at the end of a video's URL (after v=).

For example, what you need is underlined here: youtube.com/watch?v=T_MYyc-PtH4

Paste the code into the Youtube tags and it should look something like this:



This will embed a video like so:



Note: if the channel owner has disabled embedding for the video, it won't work.