Hi pw9571, yes, actually, there is a preference for that, but you need to dig a bit for it. I'm going to show all three of these related preferences:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(2) In the search box above the list, type or paste neww and pause while the list is filtered

(3) Review/Adjust the preferences as follows:

(A) browser.link.open_newwindow - for links in Firefox tabs

This is the one that has a checkbox on the Preferences page:

• 3 = divert new window to a new tab (default)
• 2 = allow link to open a new window
• 1 = force new window into same tab

(B) browser.link.open_newwindow.restriction - for links in Firefox tabs

By default, if a page sets width, height, or toolbars for a popup, Firefox will let it be a separate window. To force those into a tab as well, you can change this preference to 0:

• 0 = apply the setting under (A) to ALL new windows (even script windows with features)
• 2 = apply the setting under (A) to normal windows, but NOT to script windows with features (default)
• 1 = override the setting under (A) and always use new windows

(C) browser.link.open_newwindow.override.external - for links in other programs

• -1 = apply the setting under (A) to external links (default)
• 3 = open external links in a new tab in the last active window
• 2 = open external links in a new window <= Try this one
• 1 = open external links in the last active tab replacing the current page

To return to normal if things go haywire, right-click each "modified" preference and choose Reset.

Success?

Thank you! Option C was what I was looking for, and it worked.  ;-)

Hey there, i would like to have the same behaviour of firefox windows on a firefox on a mac for opening pdf files within a new tab in the same window.

I tried the following two options without success:

browser.link.open_newwindow: 3 browser.link.open_newwindow.override.external: 3

and

browser.link.open_newwindow: 3 browser.link.open_newwindow.override.external: -1

Current behaviour is that the pdf is split in multiple parts and an infinite amount of windows is opened. Might be a bug with pdfs

How can i open pdf links in a new tab in the same window?

Hi a.schoenenwald, if opening a PDF triggers endless new tabs or new windows, this can be caused by setting PDFs to open using firefox.exe or firefox.app. The only safe setting for viewing PDFs in a tab is "Preview in Firefox". More info in these articles:

• View PDF files using Firefox’s built-in viewer
• Firefox repeatedly opens empty tabs or windows after you click on a link

Hi jscher2000, thanks for your answer. Setting firefox as PDF viewer works for me, but it opens in a new window - but i would like to have it in the same window as new tab.

setting "browser.link.open_newwindow.override.external: 3 " (open external links in a new tab in the last active window) does not do the job for me unfortunately.

Hi a.schoenenwald, where is the PDF opening from? That "external" preference is for links in other applications or files stored on your system.

If it is opening from an external source, can you tell whether Firefox is reusing the same profile or is using a different profile? Usually differences in the theme, toolbar layout, add-on selection, and other customizations would indicate something is different. You also can use the Troubleshooting Information page to see the profile path in each window to confirm that they do or do not match. Either:

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

In the first table on the page, find and compare the paths listed under Profile Folder.