I think a new beta might have been released since you posted. Any improvement with this issue?

If not:

Sometimes the settings file that stores window dimensions and positions becomes corrupted with nonsensical values. You can rename the file and have Firefox rebuild it. Here's how:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, on the Profile Folder row, click the "Open Folder" button. This should launch a new window listing various files and folders in File Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > Exit
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename xulstore.json to something like xulstoreOLD.json. If you see a file named localstore.rdf, it's ancient, you can delete it.

Start Firefox back up again. Do windows display normally again?

That mini-reset will hide the menu bar and bookmarks toolbar. You can use one of these methods to show the toolbar list and select the desired bars there:

• right-click (on Mac Ctrl+click) a blank spot on the tab bar (or the "+" button)
• (menu bar) View > Toolbars
  On Windows, tap the Alt key to activate the menu bar temporarily.
• in Customize mode > Toolbars button (see: Customize Firefox controls, buttons and toolbars)

To turn on the Bookmarks Toolbar, Menu Bar, or other bars, click it on the list.

Hi jscher2000,

Thanks for the info. I do indeed have the latest update to 68b6. I have tried the method you suggested to reset things; however, this issue still remains.

When I set the cursor at the top of the Firefox window border so that the cursor turns to a double vertical arrow, and the double click. The Firefox window goes to full height, but not width.

Closing and restarting Firefox results in an upper window border that is slightly above the screen edge. The bottom of the Firefox window is now slightly above the screen bottom edge.

The whole Firefox window is shifted about 2 pixels upwards.

I can manually set the Firefox window 1-2 pixels down from the upper screen edge and above the lower screen edge. This Firefox window size will be set and remembered correctly. Just not a full screen vertical size as set via the method described above.

Firefox is the only program I have that won't remember a vertical window size set by the first method.

Cheers.

Oh, I wasn't aware of that method of sizing a resizable window. In a single restart test with Firefox Developer Edition, the window re-opened with the same top position, but the bottom border did not extend all the way to the task bar; I lost some height. ??