From any firefox website? Do you have an example of which webpage this is happening on? Does it still copy if you right click -> copy then try pasting it?

Let me know.

I have a single click mouse, so, no. It happens on every webpage I have tried it on AND I can not copy from the address bar.

On Mac, if you have a one button mouse, you can use Ctrl+Click for the right-click context menu.

You also could try the Edit menu on the menu bar (for selections in page content).

Tried it--it doesn't work, still can't copy anything. I can copy from Safari and Chrome webpages.

Can you paste into Firefox or is that broken too?

Have you done a normal shutdown and restart of your Mac since this problem began? That would hopefully resolve a failure to communicate between Firefox and MacOS.

On Mac there should also be a long press setting for the left mouse button to open the context menu.

You can look at these prefs on the about:config page.

• ui.click_hold_context_menus
• ui.click_hold_context_menus.delay (def:1500msec)
• System Preferences -> Accessibility -> Mouse and Trackpad -> "Enable Mouse Keys"

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Shut her down and waited several minute to start up. Problem persists.

I tried the right click copy, nothing changed.

I may have to go back to Chrome

You could try reinstalling Firefox. I think this involve dragging the application to the trash and then installing from the DMG file again. However, that's very second hand since I'm a Windows user.

I just reset Firefox, but the problem persists. I guess the next thing is to reinstall it.

I reinstall FireFox and it now works.

Hello John,

I think you might have done something wrong in FF settings. As not it's fixed, well.

Welcome to Mozilla family.

I soled the problem. I wish to know how the problem developed.