Consumers today access content and transact across different platforms and devices, but marketers are still missing out on opportunities to address this cross-platform audience, due in part to technical challenges as well as traditional concerns.

Mobile currently contributes 30% of worldwide online retail sales, with Asia leading the market. In Japan and South Korea, mobile shopping accounts for more than 45% of online retail transactions, according to Yuko Saito, Criteo's Southeast Asia managing director, citing internal stats. The retargeting company expects this number to reach 40% globally by the second half of this year.

In Southeast Asia, 36% of e-commerce traffic was on mobile devices, which accounted for 23% of total online sales in December 2014.

While it clearly offers tremendous opportunities, mobile also poses several key challenges. For one, it has spawned four different realms where consumers access content via mobile web browsers as well as in-app, or mobile apps, and they also do so via two platforms: Google Android and Apple iOS.

Saito further noted the lack of industry standards. For instance, there is no equivalent of a URL for mobile apps, which is necessary to direct users to campaign sites.

In an interview with Indian newspaper The Economic Times, Unilever's CMO Keith Weed had expressed frustration over how there has yet to be a "killer ad format" for mobile. He also noted that mobile had the potential to be a formidable "mass and custom" marketing vehicle, but said the industry had little alignment across delivery models, telcos, and mobile web browsers.

Asked for her thoughts, Saito told ExchangeWire that while she agreed mobile ad designs left much to be desired, this would soon change with users spending more time on smartphones and ad budgets moving to the mobile platform.

She said publishers were developing bigger ad sizes and offering various functions to improve user experience, such as ads that expanded when users placed their finger on them. She added that smartphones were now available in increasing size diversity, with bigger screens and mini-pad sizes, offering further improvements in ad formats.

Elaborating on what was still lacking in the ecosystem, Saito said: "The technical challenge has been resolved, so the bigger barrier going forward is educating the client. Top retailers understand the importance of mobile and already working on it, while smaller clients understand the importance, but don't have the resources to act on it.

"Another challenge is attribution, which is very important in performance marketing because it tracks conversion rates. Most of the tracking done today is through cookies and last-click. However, with cross-device marketing, we can no longer just talk about cookies because we're dealing with mobile apps."

Cookies can still be used if access is web-based, for instance, when mobile browsers are used to access websites. The challenge is when consumers access content or make transactions in-app, where cookies cannot be used, so user behaviour cannot be tracked.

To address this, Criteo uses SDKs (software development kits) to access a different type of identifiable data. According to Saito, there are no limitations when SDKs are used and they serve the same purpose on mobile apps as cookies on websites.

She said consumers now are moving fluidly across devices, resulting in changes in cookies at anytime as they move from desktop to mobile or from Google's Chrome to Apple's Safari. More savvy consumers can also delete cookies, affecting the tracking of their browsing or online purchasing behaviour. Tracking is also affected when users change devices.

"As an industry, we need to think about attribution and move to a more user-centric rather than device-centric approach. It's more easily said than done, obviously, so this is a huge discussion point in the industry," she noted.

Criteo itself is looking to improve cross-platform marketing by expanding the way it identifies users.

Need for cross-device retargeting

It is no longer uncommon for users to own multiple devices, according to Saito. Singapore consumers, for instance, use an average of 3.3 devices each--one of the highest in the world.

As such, it is increasingly important to be able to track users as they move across different devices.

Citing an internal analysis of 2,000 Criteo advertisers, covering 86 million users, Saito said 15-20% of sales were cross-device. This meant that consumers could browse for products on their work computer and would later see a related ad on their mobile phone, where they would click on the ad and purchase the recommended product.

However, to push the right ads to the right user, advertisers must first be able to properly identify the correct user. The customer ID is typically used to achieve this, but its effectiveness is limited and the customer has to be logged onto the site on each platform--for example, to their Amazon user account on their desktop as well as mobile phone - before the consumer can be properly identified.

To improve retargeting across platforms, Criteo is looking to extract other user identifiable information from its clients, which are then encoded and anonymised. "We put the data into a Criteo data cloud and share it with advertisers who contributed such information to the database," she said.

These clients are then able to tap this shared information pool to track the behavioural patterns of users as they access websites and apps across their various devices, and push relevant ads even as they move across devices. Data sharing is limited to users who have been matched up using the cross-device identifiers.

Multiple types of identifiers are used, but Saito declined to elaborate on what these might be. "It's encoded and irreversible, so it's stored as anonymous data, but enough for us to match users across different devices. We don't collect names and we don't store or use personally identifiable information.

"It's fully transparent, so users can understand why they're seeing a particular banner and they are given several opt-out options, including from the current device and all devices matched to the user's identifier data," she explained.

The data is encoded with a standard algorithm that enables Criteo to match the user across devices and powers the company's prediction engine. As more data is fed into the engine, the better and more accurate the recommendation users receive.

One challenge the company faces is convincing its clients to provide personal identifier data, due to common concerns about sharing such information with others, Saito said, noting that some companies remain conservative about the use of such data.

She added that Criteo does not offer incentives or rebates to encourage more clients to share user identifier data, preferring instead to convince them that it is safe to do so and that their customer data will remain anonymous.

"We believe that making sure we hold ourselves to the highest privacy standards, and assuring clients that we only use identifier information in their encoded form, is the best way to tackle this issue and we are making good progress so far."

Criteo started collecting user identifiers--beyond the basic customer ID--in December 2014 and has ongoing discussions with advertisers about collecting such data. It is currently matching users with their corresponding devices, and is already offering cross-platform retargeting services in some markets.

"Consumers have been cross-platform for quite a while now, but our industry is finally catching up," Saito said. "Now with cross-device retargeting capability, we can also attribute sales that take place on another platform."