Player or software to play .webm files

It depends on which playback program you are using in your device for playing the webm files. If you want to control the movement of the video then you have to use some program which has that capability to do it with webm files. One way is to convert them to the popular MP4 format and then run with any playback program. But as conversion takes time and is cumbersome it is to be exercised as last resort. Another option is to use the popular vlc player that is the 'vlc 3.0' version and that runs the webm files also. If the vlc installed in your device does not play it then you should uninstall this version and download the vlc 3.0 and then while setting up when it asks to select components scroll down and find out webm and tick the box against it. With this you would be able to use vlc features for controlling the movement of the video.

A webm file can be operated with Firefox, Google, Chrome, Opera etc. This can also be operated in the Safari Web Browser on a Mac. The same can be achieved in multiple ways. First of all, one has to go through VLC. Then from VLC rout, one has to search the VLC for Mac OS X and then one needs go for the plug in operation.
If one is on Mac, one can use most of the programmes supported by Windows to play the Webm file apart from free EI media player.
If one is interested to open Webm files on one's iOS device, this can be done through player Xtreme Media Player or through the VLC apparatus.
In order to use Webm file with a particular programme or device not supporting the format, one can convert the video to a file format supported by a free video file converter programme.