This Add-on Open link in new tab should do what you want.

Firefox has a checkbox to divert new windows to new tabs, but that only kicks in if the website has coded the link to open in a new window. If the site is set up to open the page in the same tab, Firefox doesn't have a built-in feature to override that.

Firefox does have these methods for sending a link to a new tab:

• Command+click the link
• If your mouse has a middle button or scroll wheel, middle-click the link
• Right-click the link > Open Link in New Tab

Or you could use an add-on like the one suggested above to change Firefox's standard behavior.

If you can't open any link in a new tab then check for issues caused by an extension.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes