De-Duplication Best Practice Guidelines

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The IAB Advertiser Standards charter states that to successfully adhere to industry guidelines, all advertisers should provide complete transparency on their de-duplication practises. Publishers require insight into how their traffic is reviewed against other online channels so they can make an informed decision about promoting an advertiser.

The following document demonstrates best practice guidelines for advertisers wishing to de-duplicate their publisher marketing sales against those from other online marketing channels.

The intention of these guidelines is to ensure advertisers meet their objectives in regards to reporting and ROI without compromising their publisher programme. The advice is relevant for established programmes as well as new launches.

What is de-duplication?

De-duplication is the process of attributing a sale to one online marketing channel on predefined conditions, these conditions will decide which tracking tag is shown at the confirmation of sale page.


Where an advertiser runs their programme on two networks, de-duplication is essential to prevent paying for the same sale twice.

This can occur when a customer has visited publisher sites from both networks, and ends up with two publisher network cookies on their computer.

Using automatic de-duplication, the advertiser only displays the tracking for the network that last referred the customer. Therefore, only one network receives notification of the sale, thus removing the need to decline duplicate sales manually at the validations stage.

What do I need to do to de-duplicate sales?

Awin recommends using a “Click Append” and setting a local cookie on the visitor’s machine when they enter the website.

A local cookie is one that is loaded onto the user’s computer by the advertiser. This can then be used to recognise the last referring channel and determine which tracking tag to display on the confirmation of sale page.

This is the cheapest, most efficient and accurate way to de-duplicate and it provides the advertiser with complete control over the logic employed.

This method is also referred to as “conditional tagging”.


Merchant X added a click append to their URL for each online channel to define where the customer had arrived from, a few of these are shown in red below: – Awin - Tradedoubler – Google PPC – Email campaign

They then wrote a script to place a local cookie on the user’s computer triggered by the presence of the click append.

They then established a rule that the click append source ID would be overwritten on a last referrer basis.

For a customer clicking through via a Tradedoubler publisher who then browses and returns via an Awin publisher the source id “?source=td” would be replaced with “?sourceid=aw”.

The tracking tag logic at the sale confirmation page would recognise the “?sourceid=aw” click append and show only the Awin tracking code, thus correctly awarding the sale to the last referring network.

All traffic must be tagged to ensure accurate cross-channel de-duplication. The last referrer wins method must be used across all channels to ensure fair de-duping.

Which online channels should I de-duplicate against?

De-duplicating sales reduces publisher conversion rates, and therefore their EPC/commissions also decline. Advertisers should therefore be cautious implementing de-duplication strategies as it could influence a publisher to promote a competitor.

We would recommend providing adequate notice to publishers prior to the implementation of any new policy, especially one that may affect performance statistics. It is important to be specific about which channels will be de-duped and explain the reasons why. Every advertiser is different and policies vary considerably across the industry.

We have provided some example policies below and also some general rules that will ensure publishers continue to support your programme.

Example Policy 1

Channels de-duplicated:

PPC Brand: No

PPC Generic: Yes

Price Comparison (advertiser’s own activity e.g/ Kelkoo): No

Display Advertising: No

Email Marketing: No

Direct publishers/partnerships: No

Other publisher network: No, there are no other networks

De-duplication rule:

Last referrer is attributed the sale

Method used to de-duplicate:

Click append with local cookie

Note : For Example Policy 1 the advertiser has only one piece of CPA activity which is the Awin programme. They have a substantial in house PPC campaign with many generic and long tail keywords which they wish to attribute referring sales purely to this channel. For other channels including brand PPC the advertiser wishes to award the publisher recognising their influence in completing the sale.

Example Policy 2

Channels de-duplicated:

PPC Brand: No

PPC Generic: No

Price Comparison (advertiser’s own activity e.g/ Kelkoo): No

Display Advertising: No

Email Marketing: No

Direct publishers/partnerships: Yes

Other publisher network: Yes

De-duplication rule:

Last referrer is attributed the sale

Method used to de-duplicate:

Doubleclick floodlight tracking tag

Note: For Example Policy 2 the advertiser uses a 3rd party solution to de-duplicate sales, they wish to reward the publisher's influence on the sale wherever possible. They are happy that a CPA rate be paid in addition to a CPC given the customer spent time on the publisher’s site and subsequently browsed.

This advertiser however has another publisher programme as well as some direct partnerships. These are all also rewarded on a CPA model. The advertiser cannot pay the higher CPA cost twice, and therefore they must de-duplicate the sale to the last referrer.

Example Policy 3

Channels de-duplicated:

PPC Brand: Yes

PPC Generic: Yes

Price Comparison (advertiser’s own activity e.g/ Kelkoo): Yes

Display Advertising: Yes

Email Marketing: Yes

Direct publishers/partnerships: Yes

Other publisher network: No, there are no other networks

De-duplication rule:

Last referrer is attributed the sale

Method used to de-duplicate:

Tagman container tag

Note: For Example Policy 3 the advertiser is using another alternative 3rd party solution to de-duplicate. They have decided to de-duplicate against all online channels.

They only ever want to attribute a sale to one channel. As a result of this they pay a higher commission to publishers as they do not need to factor in duplication costs.

Further recommendations

• Do not de-duplicate against Brand Paid Search (PPC)

This is one of the most common methods customers use to return to a site. Therefore, Brand Paid Search are more likely than any other channel to capture the last click, even when other channels have interacted with the user further back in the chain.

Advertisers need to consider the complex nature of the buying process, and the value of publisher involvement.

De-duplicating against brand PPC discredits the value advertisers place on their affiliates and is seen as unfair practice. If the customer has taken a little more time to decide on their purchase and subsequently typed the brand name into a search engine, it is felt that the search activity cannot be 100% responsible for that sale.

Publishers are understandably reluctant to promote advertisers who adopt this strategy. Ultimately they will experience far superior conversion rates on advertisers who do not de-dupe against brand PPC so will see greater value in sending their clicks elsewhere.

• Do not de-duplicate against display advertising

Display campaigns are typically tracked on post click sales as well as post impression sales. This is to account for the influence the banner might have had for someone simply viewing the advert as well as clicking on it.

Banner campaigns tend to run across portals with high traffic, such as Hotmail, Yahoo and MSN Messenger. Much like a customer returning via a brand keyword, there is also the chance that a customer already influenced by a publisher sees and clicks on a banner for the same advertiser whilst searching the web.

Again, it is felt that this action alone was not 100% responsible for achieving the sale. It is even less likely where an advertiser tracks post impression – the banner may have been on the page below the fold so the customer may not have seen it.

Programme Terms & Conditions

All advertisers are required to provide programme Terms & Conditions which should be added to their profile page Terms tab.

A section of this Terms tab is devoted to de-duplication where the advertiser must confirm whether they have a de-duplication policy in place and if so what other online channels publisher traffic is deduped against.


File:Terms 2.jpg

This information is then made available for publishers to view and compare against other similar advertisers in the sector. It is advisable to have a discussion with your network contact to ascertain if your de-duplication policy is too restrictive as this will hamper efforts to optimise the publisher channel.

Summary of Key Points

- Use a click append and local cookie solution to control sale de-duplication

- Consider the impact of de-duplicating against PPC and Display activity

- Be mindful of the influence a publisher can make on your customers purchase decision making

- Display your de-duplication policy within your programme Terms tab

- Communicate any changes to your policy in advance of your programme


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