SpyPig: Free email tracking system - Find out when your email has been read by recipient!


SpyPig is a free email tracking tool that lets you know when your recipient opens your email.

SpyPig Requirements

Both you and the recipient must use an HTML-formatted email, not a plain-text or rich-text formatted email. SpyPig works by using a tracking image (a SpyPig image) whose address to its remote location on our server is embedded into your email message. When the recipient opens your email, the tracking image is downloaded from our server, triggering the "email opened" alert on our system.

Microsoft Outlook and Outlook Express Users (click here)

SpyPig General Limitations

SpyPig relies on the image download as the tracking mechanism and on email as the delivery method for your notifications. Therefore, there are some limitations:

  • Insensitive Pig

    There are times when SpyPig does not know if the email has been opened. That's mainly due to the failure of the tracking image from being correctly downloaded by the recipient's email program, hence no "email opened" alert being sent to SpyPig. Contributing factors may include the following:

    • You or the recipient uses a plain-text email or rich-text email instead of HTML-formatted email
    • You use an HTML email, but somehow your email application turns the SpyPig tracking image into an "inline attachment" instead of a downloadable remote image coming from our server (See "Tested Software" below)
    • The recipient disables or blocks the automatic image download on their email application
    • The recipient's firewall, anti-spyware, anti-virus, anti-spam or anti-whatever software may mistakenly block or alter your email's source code that contains a code for the downloadable SpyPig image (See "Tips" below)
    • Your or the recipient's email service provider or network does not allow a downloadable image in the email and it deletes or alters it somehow. This usually happens if you or your recipient is in a secure corporate environment
    • Your recipient's email application stores the downloaded images in his/her computer, a process called caching, and when he/she opens your email again, his/her application simply retrieves the image from the cache instead of downloading it again (SpyPig codes tell email applications not to cache the tracking image, but some of them may ignore the instruction)
    • and so on

  • Overreacting Pig

    SpyPig sends you a notification every time your email is opened (or whenever the SpyPig tracking image is downloaded to be exact). That means the following situations may also result in you getting a notification:

    • You yourself open your own email perhaps from the Sent folder
    • The recipient opens your email multiple times
    • The recipient responds to your email by opening a new message window with your original message enclosed, including the SpyPig image (hence another image download that triggers the "email opened" alert), and after he/she sends the email back to you, you open it (yet another image download)
    • The recipient forwards your email to others and they open your email
    • In some cases, the recipient's email application, for some unknown reason, would keep downloading the SpyPig tracking image repeatedly, resulting in you getting a flood of notifications all at once. [Update: Now we limit the tracking frequency to maximum 1 notification every 5 minutes. You can change this option through the link in your notification email.]
    • and so on

    For these reasons, users get up to SPYPIG_MAX_NOTIFICATIONS_PER_TRACKED_EMAIL notifications per tracked email.

Recipient's Geographic Location

SpyPig can tell you where your recipient is located geographically when he/she opens your email. The accuracy is approximately 98% on the country level and 70% on the city level for US cities. The accuracy for non-US cities varies. This database is updated constantly to improve or maintain accuracy. The location information is based on the recipient's computer IP address. Some computer users might hide their true IP address and use a different address to appear as if they're located in a different city or even country!

Group Emails

If you send out a group email with multiple recipients with a SpyPig in it, you will still be notified every time a recipient opens your email (up to the maximum number of the notifications you get, currently set to SPYPIG_MAX_NOTIFICATIONS_PER_TRACKED_EMAIL per tracked email), but you will not know which recipient. To track each recipient, send a seperate email message with a different SpyPig.


Many email applications disable automatic image download by default, especially for emails coming from strangers they've never seen before. So you'll probably have a better chance to get SpyPig to work with the recipients you've emailed back and forth before than with those you never have. That's because these known recipients' email applications might have already "learned" about your emails and put your email address into a less restrictive category. Many email applications enable automatic image download if the email's sender (you) is on the recipient's whitelist or safe senders list.

In addition, avoid sending a very short message or gibberish in your email along with a SpyPig image as this may be mistakenly taken as a spam by your recipient's anti-spam software.

No Notification? Check Your Spam Folder

If you didn't get your notification email, check your spam folder as it might have gone there. Make sure you add spypig.com to your whitelist or safe senders list on your email application to avoid having your notifications blocked.

Because SpyPig uses email to deliver the notifications to you, sometimes the unexpected happens. Here are the possible email errors you might experience:

  • Your notification is sent to your email application's spam folder, as mentioned above. (Please add spypig.com to your whitelist or safe senders list to avoid this)
  • Your notification is sent to the wrong sub-folder in your inbox because of the email filters you use
  • You entered a misspelled email address of where the notification would be sent to when creating the SpyPig tracking image.
  • Your mailbox is unavailable (e.g. full or out of service) when the notification arrives
  • Your email service provider (e.g. AOL, GMail, etc.) rejects emails coming from spypig.com, mistakenly thinking they were spams. (Please add spypig.com to your whitelist or safe senders list to avoid this)
  • Your notification gets delayed by hours or even lost somewhere on the Internet
  • Your email application has a problem retrieving messages for your inbox
  • Our system experiences an overload and fails to send out the notification. This sometimes happens on the busiest days of the year, such as around the Thanksgiving and Christmas holidays
  • and so on

Tested Software for Email Senders (You)

SpyPig has been tested with Internet Explorer 6, Firefox 3 and 2, Safari 5, Outlook 2003 and Web-based email clients (e.g. Yahoo! Mail, GMail, Hotmail, AOL Mail, etc.) on Windows 7, Windows XP and Apple MacOS 10.6.5 operating systems (OSs). It has not been tested with other software and on other OSs (e.g. Linux, etc.). That doesn't mean SpyPig won't work on those programs or OSs. It may still work perfectly. Just give it a try by sending yourself an email with a SpyPig in it.

For the technically inclined, you also can check whether SpyPig will work for you by directly looking into the source code of your HTML email:

  1. Copy and paste the SpyPig tracking image into your email by following the instruction in SpyPig Factory.

  2. View your email's source code and locate the <img> tag for the SpyPig image.

  3. If the src value contains http://www.spypig.com like this:

    <img src="http://www.spypig.com/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxx/pig.gif">,

    then the SpyPig image has been embedded correctly. You're OK. This HTML code shows the reference (or the Internet address) of the SpyPig image as a downloadable remote image coming from our server. (Note: Some Outlook Express users would get this code correctly but still would not get the notifications if the recipient is also using Outlook Express or Outlook. See note above for Microsoft Outlook users for a possible fix.)

  4. But if you see cid in the src value like this:

    <img src="cid:xxxxxxxx-xxxxx-xxxx-xxxx-xxxxxxxxxxxx@my.isp.com">,

    then it won't work. Your application has turned the SpyPig image into an inline attachment as opposed to a downloadable remote image.

    An inline attachment means the image file itself, not its Internet address, will be sent out as part of the email message, just like when you attach a file onto your outgoing email message. When displaying this image, your recipient's email program will simply display the attached file instead of downloading it from our server, therefore no "email opened" alert will be triggered.

  5. Any other types of the src values will also not work. Only the one shown on Number 3 above will. Keep playing around with your email application or browser. It may have a hidden feature or a workaround to keep the SpyPig image as a downloadable image, as in the case of Outlook above. Also, test different ways of copying and pasting the tracking image into your email.

  6. When you're testing SpyPig, it might be easier if you change the setting for Tracking Frequency from Selective, which is the default, to Regular. Selective Tracking counts multiple "email opened" alerts in a 5-minute period as 1 and sends you just 1 notification. Regular Tracking sends you a notification every time the "email opened" alert is triggered. You can change the setting from the Tracking Settings button in your notification email.
Tested Software for Email Recipients

You don't need to be concerned with the software your recipients are using to read your emails. As long as it can correctly download the SpyPig tracking image on the emails you send them, SpyPig should work.

Still Not Working? Send Us a Test Email

If you've followed the instruction and you still don't get the email notification, feel free to send a test email to our address at . Please let us know what Internet browser, email software and platform (Windows XP, Mac, etc.) that you're using. We'll take a look at your email and give you a feedback.

Privacy Policy

SpyPig cannot read the content of your email message or know what your recipient's email address is. The email address you provide to us is solely used to send you the notifications and/or as your username for login purpose. We will not send you any junk mail. We do not sell, rent or give away your email address for any purpose to anyone. For more information, visit our Privacy Policy.

"I know you've read my email!"™
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