Simplesat surveys include an invisible tracking pixel embedded in your surveys that detect each time your customer opens an email.
We use this data to calculate the response rate. When the tracking pixel is triggered (image downloaded), we conclude that the survey was opened. The response rate is calculated by:
Response rate = (# of opens) / (# of responses received)
In some cases it's possible for a customer to respond to a survey without "opening" the email. This can happen in some tools like Outlook where images (including the Simplesat tracking pixel) aren't fully downloaded before a customer clicks on a rating. For situations like this, we count that response as an open as well.
Note: The response rate percentage is just an approximation of how frequent your clients open the email as they have a way of previewing the email without being detected by the tracking pixel.