LinkCleanhttps://example.com/article?utm_source=mailchimp&utm_medium=email&mc_cid=abc123def4&mc_eid=78fa90ce21
After LinkCleanhttps://example.com/article
mc_eid
Email marketing · Mailchimp · introduced ~2007
What mc_eid actually identifies
Mailchimp generates a unique mc_eid per subscriber per list — it's their internal “email ID”. When that subscriber clicks a link in a Mailchimp newsletter, mc_eid rides along on every outbound URL. Mailchimp's tracking pixel then ties the click to *the exact subscriber* it was sent to.
That's different from utm_source / fbclid / gclid. utm_source identifies the campaign; mc_eid identifies *the person*. It's the subscriber's surrogate identifier — a 1-to-1 token bound to an email address.
What forwarding mc_eid actually leaks
If you forward a Mailchimp newsletter link to a friend with mc_eid still attached and they click, Mailchimp records a click tied to *your* subscriber ID — from your friend's browser. Now Mailchimp has noise in your engagement profile (someone-other-than-you clicked “your” email), and on their side, they may be cookied or pixel-tagged in a way that joins back to your email-address record on Mailchimp's books.
Same shape applies to mc_cid (Mailchimp's campaign ID, which is less sensitive — names the campaign, not the recipient) and the older _mc_* family.
Why this is more aggressive than stripping utm tags
utm_source broadcasts marketing context. mc_eid is a per-person token. The harm model is different and stronger: forwarding mc_eid leaks a token that joins back to your email address, which is one short step away from your real-world identity.
LinkClean strips mc_eid as default-on, same as utm_source and fbclid — but if you're forwarding newsletter links a lot, this is the parameter that's most worth knowing about.
How LinkClean removes it
mc_eid + mc_cid + mc_tc (Mailchimp's tap-target ID) all ship default-on in LinkClean's email-marketing catalog. Same pipeline as the ads catalog — stripped on every host. The Drip equivalent (__s), Klaviyo's _kx, and HubSpot's _hsenc / _hsmi are also in the email-marketing catalog by default or on opt-in.
Frequently asked
Is mc_eid personal data?
It's tied to your email address on Mailchimp's side — a 1-to-1 token. From their perspective, yes; it identifies the subscriber the newsletter was sent to.
Will the article still load?
Yes. The destination site doesn't read mc_eid. Only Mailchimp's tracking pixel does, and that's their analytics — not part of the page.
Why is mc_eid worth stripping more than utm_source?
utm_source describes the campaign. mc_eid identifies the specific subscriber the email was sent to. The blast radius if you forward it is bigger.
Does LinkClean strip other newsletter trackers too?
Yes — mc_cid, mc_tc (Mailchimp), __s (Drip), _kx (Klaviyo), and HubSpot's _hsenc / _hsmi are in the default or opt-in catalogs depending on how vendor-specific the name is.
Clean tracking on iPhone, in one tap.
LinkClean strips ~80 vendor-specific tracking parameters from any link, from any app's share sheet — and preserves functional ones like hl, t (YouTube timestamp), and q (search). No account, on-device.
