When I am on a SE site on the stackexchange.com domain, and go to a site with its own domain such as MathOverflow, Ask Ubuntu, or Server Fault using the links in “Your Communities” or “More Stack Exchange Communities” under the right-most menu on the top-bar,

Link to MathOverflow from the top-bar menu

I do not end up with the usual https://mathoverflow.net URL, but with a strange URL such as


The string is different each time. The same happens when I go from MathOverflow to MathOverflow Meta or vice versa, but not when I go to sites on the stackexchange.com domain.

I’m using Firefox 105 on Linux; I checked it also happens in Chromium. Another user reported he could not reproduce it, so it may depend on some settings.

What is the meaning of this? Is it a bug?

Originally reported on MO meta, but I’m reposting it here after realizing it does not affect only MathOverflow.

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    Fun fact: while they use such links themselves, the * in them don't play nice with SO chat i.sstatic.net/Bwh4j.png Commented Sep 23, 2022 at 15:27
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    @V2Blast what exactly is under review? Exempting the links in the site switched from GA4 so it won't add the parameters? Commented Sep 29, 2022 at 8:06
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    @ShadowTheKidWizard: I'm not sure what you're asking. I only added the [stack-exchange-button] tag. Assuming you're asking why Catija (not me) added the [status-review] tag, adding the [status-review] tag creates an issue in our internal tracker, which we can then direct to the relevant person/team to post an official answer from staff.
    – V2Blast
    Commented Sep 29, 2022 at 9:24
  • @V2Blast oops, lol, didn't think to check revisions, it's rare that more than one staff member tagging something in such a short while. It's not "why" it's more "what is the bug you consider fixing", but guess that's up for the next level, i.e. the developer who'll get assigned to take a look on this. Commented Sep 29, 2022 at 9:47

1 Answer 1


This is tracking parameter most likely related to the change from Google Analytics 4 (GA4) upgrade

The tracking parameter is added by Google Analytics to cross-domain links. On the Stack Exchange sites, this happens when you have performance cookies enabled. An adblocker or other privacy browser plugins might also stop this behaviour even with the performance cookies enabled.

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    So ... we "won" the Cookies war. What is next? Ban URLs?
    – rene
    Commented Sep 23, 2022 at 14:48
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    Oh dear. Indeed, the parameter disappears after disabling performance cookies. Thanks! Commented Sep 23, 2022 at 14:58
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    What does this have to do with performance? Commented Sep 23, 2022 at 15:58
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  • @CodyGray they were first classified as essential, so your only opt-out was not to use SE. Them being perofrmance is second best I think
    – Luuklag
    Commented Sep 23, 2022 at 18:43
  • Yeah, I agree that a misleading name that at least serves a useful purpose is better than a misleading name that does the wrong thing, @Luuklag. But maybe there is a third option that doesn't involve using a misleading name? Commented Sep 24, 2022 at 0:53
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    @CodyGray well, by tracking clicks on links, SE can know which links are used, and which are not. Based on that they can remove unused links, or make changes to try and improve them so more people will see and click them. Guess this can fall under "performance", in some wider definition. Commented Sep 29, 2022 at 7:55

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