• by Gavin O'Malley , Staff Writer @mp_gavin, February 21, 2019

If you’ve checked your Instagram feed lately, you already know that in-app video ads are on fire.

Industrywide, the ad format saw more than 200% growth from the fourth quarter 2017 to the fourth quarter 2018.

That’s according to PubMatic’s latest Quarterly Mobile Index, which found mobile’s share of global video ad spending reached 47% in 2018 -- a massive increase from 17% in 2017.

In the fourth quarter of 2018, mobile devices accounted for more than half of all video ad spend (56%), which was way up from 19% during the same period in 2017.

But video is only part of the story.

According to the sell-side platform’s latest Mobile Index, header bidding is also having a serious moment.

The technology’s appeal is that it lets publishers offer ad inventory to several exchanges at once before calling up their ad serves. Within in-app environments, header bidding impression volumes has grown more than 300%, from 2017 to 2018.

Newer ad technologies like server-side (S2S) header bidding are beginning to take hold, per PubMatic’s latest findings. That growth is being offset by continued quality concerns, which are driving buyers to rely on private marketplaces for in-app inventory.

For example, while the mobile Web saw a rise in OpenRTB transactions, in-app inventory experienced relatively flat growth in OpenRTB, from late 2017 to late 2018 -- although private marketplace impression volume grew by 78%.

Marketers’ concerns are well founded. Double Verify has estimated that in-app ad fraud grew by as much as 800% from 2017 to 2018.

For its findings, PubMatic’s data analytics team analyzes over 12 trillion ad bids on a monthly basis.

In-app advertising now represents the majority of mobile spend on the PubMatic platform.