What is a Conversion?

Conversion is the generic term used for an action or acquisition completed on a CPA campaign. Basically if you are trying to track something like how many sales an online ad has generated, a conversion is when the thing that you want to happen, happens.

The term comes from the idea of converting a potential customer into an actual customer. The word sale isn’t used, as it can mean anything that an ad was trying to get a user to do. This includes a sign-up for an email list, a purchase of a product or download of an app.

There are words which specifically refer to the different types (eg in the previous examples: lead, sale, download), but conversion is the umbrella phrase used.

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Technical Information

You often need a Conversion Pixel in place for tracking purposes. This can often be a bit fiddly because it requires putting code directly on to a site’s confirmation page to work.

Tracking isn’t as simple as seeing how many people clicked on an ad and then immediately made a purchase either unfortunately. This would be unfair to the publisher hosting the ad. This is because many people are convinced by ads to make purchases (for example). They do not always make the purchase at that exact moment however.

This is why Post-Impression and Post-Click Windows are usually agreed between the publisher and advertiser. These mean the amount of time after an ad is seen or clicked on (respectively) that an ad still counts as having made that conversion.

Of course many users will see an ad multiple times on multiple sites before making a purchase. It wouldn’t be fair on the advertiser to have to pay multiple times for a single sale. The rule of thumb is that the last website an ad was clicked on or seen usually gets paid. This attribution model is known as “Last Click”.

Therefore advertisers usually get the finally say on how many each publisher has actually made. They do this by putting all the data they have about where every lead, sale, download etc has come from through a process called de-duplication.

Publishers can try and increase how likely ads on their site(s) are to generate leads, sales, downloads etc by optimising towards CR. However this is often quite a fraught process, due to the nature of CPA campaigns.


Other names for Conversion (synonyms)

Acquisition, Action


Not to be confused with




Conversion Definition


Find out more

Author: Justin Driskill

Justin is the founder of The Online Advertising Guide and a freelance Digital Projects Manager.

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