“Flash Game Maximizer” is a free experimental addon that enables you to resize and maximize the window of Flash content and games in Firefox by clicking a button in the toolbar.

Once the extension has been installed, you will find a new button in the bottom-right corner of your web browser that turns yellow when it detects Flash. Clicking it resizes the game to fit your browser window.

The Flash content will be reloaded in the full browser window, causing it to resize along with the window. In this way you can play Flash games, or view other Flash content, in any custom size you like. This even includes the Firefox “full-screen mode” for a true gaming experience.