What Is an Email Tracking Pixel?

An email tracking pixel is a tiny, invisible image — typically 1×1 pixel — embedded in the HTML of an email. When you open the email, your email client fetches the image from a remote server. That fetch request tells the sender’s server your IP address, the time you opened the email, the device and email client you used, and sometimes your approximate location.

Marketers, sales teams, journalists, and even individuals use tracking pixels routinely. Services like Mailchimp, HubSpot, Superhuman, Mixmax, and Streak embed these pixels automatically in every email they send. The image URL contains a unique identifier tied to your email address, so the sender knows exactly when you opened their message — often to the second.

What tracking pixels reveal:

Whether and when you opened the email
How many times you opened it
Your IP address (and inferred location)
Your device type (desktop/mobile) and operating system
Your email client (Gmail app, Apple Mail, Outlook)

This data is used to time follow-up emails, prioritize sales leads, and build profiles on individuals without their knowledge or consent.

How Tracking Pixels Are Hidden

Senders hide tracking pixels using several techniques:

<!-- Classic 1x1 pixel -->
<img src="https://track.mailchimp.com/track/open.php?u=UNIQUEID" 
     width="1" height="1" style="display:none" />

<!-- Hidden in footer as whitespace -->
<img src="https://opens.superhuman.com/e/UNIQUEID.gif" 
     style="opacity:0;position:absolute" />

<!-- Disguised as a spacer image -->
<img src="https://t.hubspot.com/e1t/o/ACCOUNTID/UNIQUEID" 
     width="0" height="0" border="0" />

Modern tracking services also embed pixels inside linked images, logos, and email signatures — so you cannot simply avoid clicking “invisible” images.

Method 1: Block Remote Images by Default

The single most effective method is to disable automatic remote image loading in your email client. This prevents your client from fetching any external content — including tracking pixels — until you explicitly click “Load images.”

Gmail (Web)

Click the gear icon → See all settings
Go to General → Images
Select “Ask before displaying external images”
Click Save Changes

Gmail also analyzes images through Google’s proxy (which caches them), masking your IP from senders. However, the open event is still recorded — Google loads the image on your behalf whether you want it to or not. This protects your IP but does not stop tracking.

Gmail (Android/iOS)

Settings → your account → Images → set to “Ask before displaying”

Apple Mail (macOS Ventura+)

Apple introduced Mail Privacy Protection (MPP) in macOS 12 Monterey. It pre-fetches all email images through Apple’s proxy before you open the email, masking your IP and making your open time unreliable.

To enable: Mail → Settings → Privacy → Protect Mail Activity — check this box.

Note: MPP does not prevent tracking completely — it makes tracking less precise by randomizing open times and hiding IPs, but the open event may still be registered.

Apple Mail (older macOS without MPP)

Mail → Preferences → Viewing → uncheck “Load remote content in messages”

Outlook (Desktop)

Go to File → Options → Trust Center → Trust Center Settings
Click Automatic Download
Check “Don’t download pictures automatically in HTML email messages”

Thunderbird

Thunderbird blocks remote content by default since version 78. Verify: Settings → Privacy & Security → Mail Content → ensure “Block remote content in messages” is checked.

You can also add trusted senders who are allowed to load images without prompting.

Method 2: Use a Privacy-Focused Email Client

Tutanota (Tuta)

Tuta blocks all remote content by default with no option to enable it globally. Every email is treated as potentially tracking-enabled. Images embedded as base64 inline are shown; external URL images are always blocked.

Proton Mail

Proton Mail loads images through its own proxy servers, masking your IP. Like Apple MPP, this protects your location but may still confirm you opened the email. For stronger protection, turn off remote content loading entirely in Settings → Messages → Block remote content by default.

Fastmail

Fastmail allows you to set remote image blocking per-folder or globally under Settings → Privacy → Remote Images → Block all remote images.

Method 3: Use a Pixel-Blocking Service or Extension

MailTrackerBlocker (Apple Mail Plugin)

MailTrackerBlocker is a free, open-source Apple Mail plugin that specifically identifies and strips tracking pixels from known services (over 200 tracker patterns). It adds a banner to tracked emails showing which service tracked them.

Install via Homebrew:

brew install --cask mail-tracker-blocker

Then enable it in Mail → Settings → General → Manage Plug-ins.

Ugly Email (Chrome Extension)

Ugly Email is a browser extension for Gmail that detects tracking pixels and places an “eye” icon on tracked emails before you open them. It also blocks the pixel from loading when you open the email.

Available at the Chrome Web Store. It supports Mailchimp, HubSpot, Yesware, Streak, Bananatag, and dozens of other trackers.

uBlock Origin (Advanced)

uBlock Origin’s filter lists include rules targeting known email tracking domains. If you access Gmail via web browser with uBlock Origin in Medium Mode, many pixel URLs are blocked at the network level before they load. Add the AdGuard Annoyances list which includes email tracker domains.

Method 4: Use Email Aliasing Services

Email aliasing services like SimpleLogin and AnonAddy can strip tracking pixels before forwarding emails to you. SimpleLogin includes an option to strip images from forwarded emails, effectively blocking all pixel tracking passively.

In SimpleLogin: navigate to your alias settings and enable “Remove tracking parameters from emails”.

Identifying Tracked Emails Manually

If you view email source, look for <img> tags with URLs from known tracking domains:

Service	Tracking Domain
Mailchimp	`list-manage.com`, `mcusercontent.com`
HubSpot	`hubspot.com`, `hs-email.com`
Superhuman	`superhuman.com`
Streak	`mailfoogae.appspot.com`
Yesware	`yesware.com`, `t.yesware.com`
Mixmax	`mixmax.com`

To view email source in Gmail: open the email → three-dot menu → “Show original”.

Summary

Email tracking pixels are a widespread, largely invisible surveillance tool. The most reliable defenses are disabling automatic remote image loading in your email client, using Apple Mail Privacy Protection or a proxy-loading email service, and installing a pixel-detecting extension like Ugly Email or MailTrackerBlocker. For the strongest protection, combine all three — block images by default, use an aliasing service like SimpleLogin, and access your email through Thunderbird or Proton Mail with remote content blocked.