msclkid is the Microsoft Click ID. Microsoft Advertising adds it to a landing page URL when someone clicks a paid search advertisement, usually on Bing. It exists so that Microsoft's conversion tracking can connect the click to what happens afterwards. The page does not need it.
If you have found this parameter and were not expecting it, the most common explanation is that you clicked a sponsored result on Bing, or arrived through a search box in Windows or Edge that runs on Bing behind the scenes.
What it does
Microsoft Advertising has an auto-tagging setting that behaves almost exactly like Google's. Switch it on and every ad click gets a msclkid appended:
https://example.com/offer?msclkid=8f3b1c9d2e7a4
The value is a token identifying that click. On its own it does nothing. It becomes useful when the destination site runs the Universal Event Tracking tag, Microsoft's equivalent of the Meta Pixel or the Google Ads tag. The UET tag reads the parameter, stores it, and reports conversions back against it.
Microsoft's own documentation on auto-tagging and msclkid is reasonably direct about this, more so than most platform documentation on the subject.
Why it exists in the URL rather than a cookie
The same reason as everywhere else. Browsers restricted third-party cookies, so attribution moved into the address.
There is a Microsoft-specific wrinkle worth knowing. When the UET tag sees a msclkid, it can write it into a first-party cookie on the destination site's own domain. A first-party cookie set by the site you are actually visiting survives browser restrictions that a third-party cookie would not. So the parameter is not just carrying data, it is seeding storage that then persists after the parameter is gone.
That is not unique to Microsoft. It is the general pattern across all of these systems, and it is the reason I stopped thinking of URL cleaning as a privacy measure and started thinking of it as tidying. Removing the parameter before you share a link prevents you passing your click token to somebody else. It does not undo what happened when you clicked.
Is it safe to remove?
Yes. No page requires it.
The usual caveat applies if you are the advertiser: strip these from links you share, not from the landing pages you are testing, or you will break your own reporting and spend an hour confused about it.
How to remove it
By hand, delete msclkid and its value from the query string. If it is the only parameter, delete everything from the ?.
If the URL has other parameters that matter, removing one cleanly by hand is fiddly. Pasting it into the links cleaner on the homepage does the same job without the risk of cutting off something the page needs.
Related parameters
gclid is the Google equivalent and the one you will meet far more often. It has a longer history and more variants, covered in what is gclid.
fbclid is Meta's version, discussed in what is fbclid.
All three, plus the smaller ones, are listed in the URL tracking parameter glossary.
Frequently asked questions
Why am I seeing msclkid when I do not use Bing?
Windows search, Edge's address bar and several built-in Microsoft surfaces route queries through Bing. You may be using it without having chosen it.
Is msclkid the same as msclid?
msclkid is the correct spelling. msclid is a common typo, including in some third-party blocklists, which occasionally means the real parameter slips through a filter.
Does removing it break the advertiser's tracking?
For that particular visit, yes. It does not affect anything for you.
Should I block it or just remove it?
Removing it from links you share is the useful habit. Blocking it entirely, through a browser extension, is a personal preference and does not change what the site can observe once you are there.