# Using the Referring URL Parameter
Take the PXA course
The Referring URL is the [HTTP Referrer](https://en.wikipedia.org/wiki/HTTP_referer) value that impact.com records from the user's browser at the time of a click and is a good indicator of where traffic to your website is coming from. However, it is not 100% trustworthy or reliable as a tracking source, as it is highly dependent on how the click was made or the link was opened. There is a myriad of factors that can affect what gets sent to impact.com as the Referring URL.
#### Factors that affect Referring URL reliability
If you see clicks in the [*Performance by Referring Domain*](https://app.impact.com/secure/advertiser/engage/additionalreports/report/viewReport.report?id=5243) report with a “No referring domain" status in the *Domain* column, it often means that there is no Referring URL information available due to any of the following reasons:
* The user manually entered the site URL into the browser address bar.
* The user visited the site via a browser-maintained bookmark.
* The user opened the site as the first page in a new window or tab, such as by right-clicking a link.
* The user clicked a link in an external application.
* The user switched from a secure protocol (https) to a non-secure protocol (http).
* The user switched from a secure URL (https) to a completely different secure URL (https).
* The user may have security software installed (antivirus, firewall, etc.) which strips the referrer from all requests.
* The user is behind a proxy server that strips the referrer from all requests.
* The user visited the site programmatically without setting the referrer header (the use of searchbots).
* Some browsers’ privacy policies limit access to prevent `HTTP_REFERER` from being passed.
* The user has a browser add-on or extension that blocks it for privacy reasons.
{% hint style="info" %}
**Note:** impact.com recommends that you do not use the Referring URL option in payout groups when determining payouts to partners, and not to lean too heavily on the Referring URL as a source of data for decision making.
{% endhint %}
