Can I force Flash games to play in fullscreen mode?

You can't. Normally, a Flash object stretches to fill all space given to it in the <object> or <embed> container, stand alone Flash player window, or screen. If it doesn't, there's nothing you can do without access to the original .fla file.

You can't do so natively, but that doesn't stop you from decompiling it to get .fla files from which you can further modify.

Be aware most flash decompilers are complete dirt, so it takes quite a bit of effort to do anything useful. Even then, a given flash file is very unreadable and usually you'll end up having to build it back up from scratch using the various pieces.

All in all, it's pretty difficult to do and only somewhat legal.

This worked for me, so please try this.

Right click on the shortcut of the flash game that you wish to play full screen and then click properties. Once the properties window is open, make sure the "shortcut" tab is selected and then look for the word "Run" and then click on the drop down menu beside it and change it from "Normal" to "Maximized". Then click apply and then ok.

After that, whenever you open that game, it should automatically open maximized. Just make sure though that you always open it using that shortcut. If there is no shortcut and just only the main .exe for that game, you will need to create a shortcut first, and then after you do that, just follow the same steps that I mentioned above.

I hope this helps. Good luck :)

If you play in a browser, you culd use a bookmarklet or user script to full screen the game element. Try pasting something like this in your address bar:

javascript: addEventListener('click', function(ev) {var el = ev.target, rfs = el.requestFullScreen || el.webkitRequestFullScreen || el.mozRequestFullScreen; rfs.call(el);});

This should fullscreen a clicked element.
In some browsers (cough Chrome cough), you'll need to type the "javascript:" part yourself. Put it in a bookmark to circumvent that.

I did this:

1. Right-click taskbar > Taskbar settings > Turn on the "Automatically hide" option;
2. Download WinExplorer: http://www.nirsoft.net/utils/winexp.html;
3. Launch the Flash game as you would normally;
4. Run the winexp.exe as Administrator;
5. Click on the Style tab; Uncheck all styles except WS_VISIBLE (WS_CLIPSIBLINGS seems to want to stay checked for me too);
6. Click on the Size & Position tab; In the General section, type in Left: 0, Top: 0, Width:(fill in your current screen width divided by any scaling applied - for example, for me it's 2160/1.5), Height:(fill in using current screen height divided by any scaling);
7. Click Modify button;
8. Close the WinExplorer;
9. Go back to the game window (Alt-Tab, etc.);

The game window should be full screen now. If you right-click desktop > Display settings, you can view your screen size and scaling.

There are games that allow you to open in full screen, there are games created by the developer that it doesn't respond so when you open the whole screen it doesn't grow.

If you are playing in Browser, use this script; https://greasyfork.org/en/scripts/4870-maximize-video

Back when I played lots of Flash games, many implemented a protection in form of an exact window/frame size specification to prevent/discourage hotlinking for example.

Code like that for example would be a big problem for your plan.

I.e. the game would actually display a piracy warning if played at an incorrect resolution. Some would actually go as far as not doing anything besides displaying said warning.

Pressing F11 (Fn + F11 on some keyboards) will fullscreen the HTML element, therefore making the entire game fullscreen.