Is it possible to quickly restart Firefox Quantum (V57 or up)?

Solution 1:

Two-Click Solution

Firefox Quantum has a restart button. Here's a way to make it accessible so you can restart with two mouse clicks (and no add-on required).

Type about:profiles in the URL window. This opens a profiles dashboard. You can do all kinds of profile-related things (even launching another Firefox instance with a different profile); it's a generally handy tab. At the top are two restart buttons, one to restart normally and one to restart with add-ons disabled.
Right-click on the tab, and select Pin Tab. This will move the tab to the left end of the tab bar and affix it there as a miniature tab with just the Firefox icon. It will always be there until you decide to unpin it.

To restart with two clicks:

Click on the pinned tab.
Click the Restart button.

Regardless of whether you have Firefox set to restore the previous session on startup, you will be back where you left off after restart; restart restores the session.

Solution 2:

Ctrl+Shift+J to open Browser Console, then Ctrl+Alt+R to restart.

The restart command only works when the Browser Console window is open and has the focus. This method works out-of-the-box with zero configuration and may be the only way to restart the browser if the interface locks up (unable to click any UI elements).

Solution 3:

I want to quickly restart Firefox, not losing any tabs that are still open before the restart.

Use the Restart Browser add-on:

Allows to restart the browser with a button.

Confirmed as working with Firefox 61.0.1:

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Solution 4:

No one-click solution but for this task I suggest the use of a session manager like Tab Session Manager. Advantage: You can save different sessions for later use.

Solution 5:

Open the Browser Console (Ctrl+Shift+J)

Type BrowserUtils.restartApplication() and press Enter