Basic tracking of conversion from Adwords using referrer, is it possible? (both Ads in SERP and in Content Network)

Question

Reading in AdWords Help it seems the only way to track clicks to my site from AdWords is to use the Google code snippet.

If I don't want to use such snippet, and simply track the referrer, can we say that clicks coming from Google AdWords (either Ads in SERPs and Ads in Content Network) starts all with a certain url in the referrer?

In other words, can we say:

• when referrer is http://www.google.it/search... or http://www.google.it/url... then it's coming from organic seacrh
• when referrer is something else (tell me what) then it's coming from and Ad of AdWords

It would suffice for me to distinguish between who is coming form organic SERP and who is coming form click on Ad (I don't need to know which Ad or what keyword).

Is there something (even if non-official) that analyzed this and you could suggest me to read?!

Answer 1

It has always been possible, with varying degrees of reliability. But starting last year, most clients now search via SSL, so the reliability of the referrer field as a way to track adwords clicks is so low you might as well say it is NOT possible to use referrer for this purpose.

The reason you can't trust referrer to calculate your adwords clicks anymore: depending on the browser and platform of the client, the referrer will be blank or it will not contain the query terms (i.e., the referrer will be only "https://www.google.com").

Read more about it in this searchengineland article.