Email Tracking Pixel Detector

About the Email Tracking Pixel Detector

Many e-mails report back when you open them: a tiny picture, invisible or 1 × 1 pixel, is downloaded from the sender’s server the moment the message is shown, and its address carries a code for you. Links can be tracked too — they go through a redirect that records the click before sending you on. This detector reads a saved message (.eml, Outlook .msg or its pasted source) without loading anything from it, and finds those trackers: 1 × 1 and hidden pictures, picture addresses that carry a code or your own e-mail address, pictures from mailing services’ tracking servers, CSS backgrounds, web fonts and style sheets, and tracked links.

The result says in plain words what the sender learns, names the mailing service when the tracker shows it, and points to the setting in your mail app that stops it. With a Pro pass you also get the full list with the evidence for each tracker, a clean copy of the message (.eml and HTML) with the trackers removed and redirect links replaced by their real destination, and a scan of a whole .mbox export with a table of which senders track you. Nothing is uploaded.

Common uses

• Checking whether a sales or recruiting e-mail told the sender that you read it.
• Finding the newsletters and shops that track every open, to unsubscribe or block their pictures.
• Keeping a copy of an important message without the pieces that phone home.
• Showing a team what open tracking looks like before choosing their mail settings.

What the sender learns

When your mail app downloads a tracking picture, the sender’s or their mailing service’s server sees the request: that the message was opened and when, your internet (IP) address — which points to your area — and your mail app and device. Proton describes its tracker protection as hiding exactly these: “your personal IP address, device information, and the exact time you opened the email” (Proton Mail support). A tracked link records the click, then forwards you. Amazon SES, for example, adds a 1 × 1 transparent picture with a unique file name to each message and “can tell exactly which message was opened and by whom” (Amazon SES Developer Guide).

Stop trackers in your mail app

• Gmail (computer): Settings → See all settings → Images: Ask before displaying external images → Save Changes (Gmail Help).
• Outlook for Windows (Microsoft 365, 2024, 2021, 2019, 2016): File → Options → Trust Center → Trust Center Settings (in Outlook for Microsoft 365, the Automatic Download tab) → Don’t download pictures automatically in HTML e-mail messages or RSS items must be ticked. Outlook blocks picture downloads by default, so check that nobody turned it off (Microsoft Support).
• Apple Mail (Mac): Mail → Settings → Privacy → Protect Mail Activity: your IP address is hidden and remote content is downloaded privately in the background when the message arrives, not when you read it. With it off you can choose Block All Remote Content (Mail User Guide).
• Proton Mail: Block email tracking is on by default (Settings → Email privacy on the web; Privacy and security in the apps) (Proton Mail support).

Blocking pictures stops open tracking; it does not stop click tracking. Hover over a link, or use the clean copy, to see where it really goes.

How trackers are found

• 1 × 1 and hidden pictures: width and height of 3 pixels or less, or hidden with display: none, visibility: hidden, opacity: 0 or a zero size.
• Coded picture addresses: an address with an “open”, “track” or “pixel” part and a long code, or one that contains your e-mail address (also base64-encoded).
• Mailing services’ tracking servers: Amazon SES (awstrack.me) and SendGrid (sendgrid.net), the tracking domains their own documentation names (Amazon SES Developer Guide, Twilio SendGrid docs).
• Other things fetched when the message is shown: CSS background pictures, web fonts, style sheets and @import rules.
• Tracked links: links through a tracking redirect, Mailchimp’s and Constant Contact’s click tracking included (read with the Safe Links Decoder’s engine, which also recovers destinations written inside redirects), links on the same server as the tracking picture, and links that carry your address.

Outlook’s conditional sections (<!--[if mso]>) are checked too, because Outlook shows them. Nothing in the message is loaded or run.

Limitations

• Trackers are recognised by what they look like. A tracking picture that looks like an ordinary photo, on an ordinary address, cannot be told apart — so every picture from the internet is counted, and the clean copy can remove them all.
• Some links keep their destination on the tracking server; those cannot be unwrapped without opening them, which this page never does.
• Mail apps and webmail may load pictures through their own proxies, change links or block trackers before you see them; a message saved from such an app may already be changed.
• Messages larger than 40 MB in an .mbox are counted but not checked.

Privacy

On this device: nothing is sent

Messages are read in your browser and never uploaded; nothing in them — pictures, fonts, links — is ever loaded. Mailbox exports are read in a background worker, a piece at a time.