KB0033: Using Qualoupe with multi-process Firefox (v48 or later)


Since version 48, Firefox has defaulted to a multi-process mode for some users (whether or not it’s enabled depends on various factors). Multi-process mode runs different parts of the browser in different “processes”, which makes better use of modern multi-core chips.

Unfortunately, in migrating to multi-process mode, the Firefox developers have broken some functionality that Qualoupe relies on. We have raised an issue on their bug tracker, but it looks unlikely that they will address it. This means that to run Qualoupe on Firefox 48 or later you may need to disable multi-process mode.


The most obvious symptom of this issue is that menus or other pop-ups (such as lookup boxes) fail to open in Qualoupe. If you experience this, you should continue to confirm that you have multi-process mode enabled, and then disable it to continue using Qualoupe (or switch to an alternative, as described at the bottom of this article).


To see whether or not multi-process mode is enabled, follow these steps:

1) Type “about:support” (without the quotes) into your browser’s address bar and press the ENTER key.
2) In the “Application Basics” section near the top of the page you’ll find an entry labelled “Multiprocess Windows”. If this contains a value greater that 0 for the first number then Firefox is running in multi-process mode and you’ll need to disable it to use Qualoupe.

The images below show examples of this screen, first with multi-process mode enabled, and then with it disabled.

Multi-process enabled Firefox

Multi-process disabled Firefox

Note that you may have different descriptive text or numbers – the important thing is whether the first number is greater than zero.

Disabling Multi-process Mode

If you have determined that multi-process mode is enabled, you will need to disable it to continue using Qualoupe. Follow these steps carefully, as you’ll be changing a hidden configuration option, and you should take care not to change any other values:

1) Type “about:config” (without the quotes) into your browser’s address bar and press the ENTER key.

2) You’ll probably be faced with a screen titled “Here be dragons!” that warns you of the potential dangers of changing these configuration options.

3) Click the “I’ll be careful, I promise!” button to continue to the main configuration screen.

4) Enter the following text into the search box at the top of the page: browser.tabs.remote.autostart

5) The list of options will be filtered as you enter the text, until you’re left with only those that start with “browser.tabs.remote.autostart”. This may be a single entry, or there may be others, probably with a numeric suffix.

Configuring multi-process mode

6) If any entries have a value of “true” in the right-hand column, double click on them to change them to “false”. E.g. in the image above, the last line needs to be double-clicked to change it to “false”.

7) Any lines that you change will be drawn in bold, with the “Status” column listing them as “user set”.

Configuring multi-process mode - modified

8) Restart Firefox for the change to take effect, then follow the steps in the previous section to confirm that multi-process mode is now disabled.

Alternative Options

We are hard at work developing the next-generation of Qualoupe, which will work with multi-process mode enabled. We are also investigating changes to existing versions of Qualoupe that will automatically disable multi-process mode when a new browser first accesses the server.

In the meantime, apart from the changes described above, there are two other options available:

1) Use Firefox 45ESR. This is an “Extended Support Release” that does not have multi-process mode enabled. Note that future ESR versions will still require you to follow the steps above. You can find more information in this knowledge base article.

2) Use Qualoupe Runner. This is a stand-alone application based on the same technologies used in Firefox, but without the Firefox UI and without multi-process mode. Contact our customer support team for more information.


Since version 0.48 of Firefox it’s possible that multi-process mode is enabled. This is incompatible with current versions of Qualoupe. To continue using Qualoupe you must either:

1) Manually disable multi-process mode using the instructions on this page.
2) Revert to an older version of Firefox (45ESR recommended).
3) Switch to Qualoupe Runner.


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