Header bidding has grow to be the de facto strategy to programmatic advert auctions because it was launched in 2014.
When a consumer visits a webpage, header-bidding auctions happen in actual time as a web page masses, which permits all exchanges to submit bids on an advert impression concurrently.
However working so many real-time auctions requires an immense quantity of processing energy, and publishers usually have a alternative for find out how to implement header bidding.
With client-side header bidding, the majority of that processing happens on the consumer’s system within the internet browser itself. With server-side header bidding, the processing occurs on a distant server.
Listed below are the professionals and cons of every strategy and a few typical use instances.
The fundamentals
However first, a fast refresher on some programmatic fundamentals is so as.
Advert auctions begin with a bid request being despatched from the writer web page to SSPs, which run the public sale. JavaScript code working on the writer web page, often called a header-bidding wrapper, determines the principles of the public sale, together with which bidders can take part, what the minimal bid needs to be and – crucially – how lengthy bidders have to answer a bid request earlier than the public sale instances out.
Prebid offers probably the most extensively used header-bidding wrapper, and it presents two completely different options: Prebid.js, which is used for client-side auctions, and Prebid Server, which is used for server-side auctions. However there are additionally different wrappers, together with some created by particular person publishers – for instance, CBS makes use of a proprietary wrapper referred to as BidBarrel.
In the meantime, Google Open Bidding and Amazon’s Clear Advert Market are examples of server-side setups.
At this time, the overwhelming majority of header-bidding auctions are run client-side throughout the browser. Server-side header bidding is newer, extra sophisticated and dearer to arrange and preserve, and due to this fact much less established.
In a client-side public sale, the top consumer’s internet browser offers the computational reminiscence required to run the entire processes for an advert public sale – together with the entire bid requests despatched from the writer web site to SSPs.
Header bidding requires lots of reminiscence to run due to the sheer quantity of information being despatched forwards and backwards between publishers and SSPs. And the extra reminiscence utilized by the browser, the extra seemingly it’s that the webpage will take longer to load.
Publishers wish to hold their web page load time as brief as doable, as a result of customers usually tend to depart a web site if it doesn’t load shortly. Server-side header bidding was born primarily from the promote facet’s need to cut back web page load instances, stated Heather Carver, CRO at Freestar, a writer monetization platform.
In a server-side public sale, the writer web site solely makes one name to a devoted server to start out the public sale course of, which then calls the person SSPs to allow them to run their auctions. That server takes the majority of the computational load off the browser, which permits webpages to load extra shortly.
However for server-side header bidding to work, publishers should both preserve their very own server or have a 3rd get together – usually Prebid or an SSP – run and handle it for them. And SSPs can solely run server-side in the event that they’ve whitelisted the middleman server. For instance, if a writer is utilizing Magnite’s SpringServe server to run server-side header bidding, different SSPs like Index Change and Xandr need to whitelist it.
Shopper-side: Flexibility and transparency
The complexity of establishing server-side integrations means client-side header bidding makes extra sense for the overwhelming majority of writer use instances, stated Dennis Colon, head of product and technique at enterprise automation supplier JIFFY.ai. Assuming a writer is utilizing a header-bidding wrapper maintained by a 3rd get together like Prebid, he stated, a client-side strategy is simpler to arrange and doesn’t require a lot help or upkeep on the writer’s half.
Shopper-side header bidding additionally offers some advantages for SSPs. As a result of SSPs can entry the browser and drop their very own monitoring pixels on the web page, they’re capable of finding out “as a lot as they’ll inside authorized limits” concerning the consumer on the opposite facet of an advert impression, corresponding to IP tackle and the browser model used to entry the web page, stated Jared Siegal, CEO of writer tech startup Aditude.
Additionally, in a client-side strategy, SSPs have “full management” over cookie matching, Siegal stated, permitting them to search out matches between the advertiser’s viewers and that of the writer through the use of third-party cookies – whereas third-party cookies are nonetheless in play, that’s.
When an SSP has this degree of transparency, it normally interprets into greater CPMs for the writer, as a result of advertisers are keen to pay extra for audiences they know extra about.
Plus, client-side header bidding additionally provides SSPs the flexibleness to customise their header-bidding adapters, whereas the server-side strategy requires that adapters stick with OpenRTB requirements, stated Patrick McCann, SVP of analysis at Raptive and chair of Prebid.js.
In distinction, when a writer contains an SSP’s adapter in its client-side header-bidding wrapper, the SSP can customise the adapter to swimsuit the wants of its shoppers. This helps advertisers win extra of the writer’s auctions, which makes the SSP more cash.
As an example, an SSP’s client-side Prebid adapter may embrace the video.plcmt area that specifies whether or not a video placement is instream or interstitial, encouraging extra bids from advertisers which can be in search of both placement kind. Or the adapter may very well be set as much as ping the browser API for data that isn’t included in OpenRTB codecs, like a tool’s display screen dimension or connection velocity.
DSPs may also immediately combine their demand through a header-bidding adapter. For instance, The Commerce Desk’s OpenPath depends on client-side Prebid.js adapters, McCann stated.
Nevertheless, client-side header bidding doesn’t supply limitless flexibility. Every browser imposes limits on what number of concurrent bid requests may be despatched to SSPs and what number of scripts can perform on the web page, Siegal stated. And the header-bidding wrappers used for client-side auctions restrict the variety of pixels an SSP can drop on the web page, corresponding to viewability and measurement pixels. Prebid normally permits round 5 pixels per bid, he stated.
Server-side: Demand and rising channels
By way of flexibility, server-side header bidding permits publishers so as to add extra SSPs. In a client-side setup, publishers need to steadiness the demand introduced by any extra companions in opposition to the influence to their web page loading instances.
(It’s value noting, nevertheless, that many trade specialists – together with McCann and Colon – say the impact of including SSPs on web page load instances is considerably overblown, and components like damaged tags or outsized advert inventive recordsdata are the primary culprits.)
As a result of including SSPs to a server-side header-bidding stack doesn’t place extra of a burden on the browser, publishers can add an nearly limitless variety of SSPs and different demand companions, Freestar’s Carver stated.
Extra SSPs means greater bid density, which can lead to extra income for the writer – however there’s trade-off. SSPs may have much less transparency into server-side auctions, Carver added.
Third-party cookies will also be used server-side to match information units, however as a result of there’s an middleman server between the writer and the SSP, the sign received’t be as sturdy, McCann stated.
Various IDs like UID2 or LiveRamp’s RampID, which depend on discovering e mail tackle matches between advertiser and writer information units as an alternative of utilizing cookies, compensate for the sign loss in server-side setups. Various IDs will also be used client-side, however they’re not as mandatory due to the convenience of cookie-based matching when there’s a direct connection between the SSP and the browser. Subsequently, client-side integrations are way more depending on cookies and way more threatened by cookie deprecation.
Server-side header bidding can be the one possibility for media environments that don’t depend on an online browser – together with CTV (which means streaming video on a linked TV set), digital out-of-home and something app-based.
However, whereas server-side header bidding is rising in popularity and is the one possibility for sure rising media channels, it’s arguably the much less environmentally sustainable possibility. Publishers or SSPs sustaining their very own bodily servers moderately than counting on a digital occasion throughout the browser has an even bigger influence on their sustainability ranking, Colon stated.
Why not each?
Whereas every strategy has its respective strengths and weaknesses, publishers don’t have to decide on between solely client-side or server-side header bidding. Each can be utilized for a similar public sale.
It is smart for publishers to arrange client-side integrations for his or her top-bidding SSPs, Carver stated, whereas counting on server-side integrations for different SSPs. Some SSPs even carry out higher server-side, she added.
Most publishers can deal with eight to 12 SSPs working concurrent auctions earlier than they would want to maneuver extra demand sources server-side to make sure web page load instances received’t be affected, McCann stated.
The balancing act of deciding which SSPs to combine and the way has led sell-side tech distributors to supply AI-driven options that decide which SSPs carry out higher beneath a client-side or server-side setup and optimize accordingly.
However, though client-side integrations are nonetheless exceedingly widespread, third-party cookie deprecation may power a mass migration to server-side integrations as a result of it’s going to render client-side header bidding’s single largest benefit – the convenience of cookie matching – out of date.
“The second cookies are much less related,” stated Matthew Whaley, COO at Freestar, “it’s a no brainer: client-side shouldn’t even be there.”
