# mc_eid — Mailchimp's per-recipient email ID

- Canonical: https://linkclean.app/trackers/mc-eid/
- Updated: 2026-07-20
- Author: Ken Tominaga (https://ken0nek.com)
- Get the app: https://apps.apple.com/us/app/linkclean/id6758604043

Parameter: `mc_eid` · Category: Email marketing · Vendor: Mailchimp

> mc_eid is Mailchimp's per-**recipient** identifier — a token tied to the specific email address the newsletter was sent to. Forwarding it tells Mailchimp that someone else opened your email. Of all the trackers LinkClean strips, this is the one that most directly leaks identity.

## 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.

## Example

Looks like this in a URL: `https://example.com/article?utm_source=mailchimp&utm_medium=email&mc_cid=abc123def4&mc_eid=78fa90ce21`

After LinkClean: `https://example.com/article`

## 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.


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