Programmatic Flow
BetaA schematic of how an ad dollar moves through the open programmatic stack: advertisers route spend through agencies and DSPs to SSPs / exchanges, which auction inventory to publishers. Built for teaching, not for measurement.
← swipe horizontally to see all layers →
Brands buying attention.
Holding cos that plan + execute the buy.
Buy-side tech — places bids on behalf of the advertiser.
Sell-side marketplaces — run the auction, route winning bids.
Supply-side — own the inventory the bids compete for.
Walled gardens — the other half of digital advertising
The Sankey above shows the open programmatic stack. But more than half of digital ad spend never touches it. Walled gardens are platforms where the same company runs the DSP, the exchange, and the supply — there's no third-party auction. Each card below is one closed ecosystem.
Inventory: FB + IG news feed, Reels, Stories, Audience Network
Why “walled”: No third-party DSPs. Ads Manager is the only buy. No cookie-based ID exchange outside Meta's graph.
Inventory: Search results, YouTube video, Discover, Gmail Promotions
Why “walled”: Google Ads / DV360 are the buy-side; the auction is closed to outside DSPs. Distinct from Google Ad Manager (which IS in the open Sankey above).
Inventory: Sponsored Products, Sponsored Brands, Amazon DSP for Prime Video
Why “walled”: On-Amazon inventory only auctioned via Amazon Ads. Sponsored placements live entirely inside Amazon's retail funnel.
Inventory: For You feed, Spark Ads, TopView
Why “walled”: TikTok Ads Manager is the only DSP. Limited third-party measurement (mostly internal Pixel + a few approved verification vendors).
Inventory: App Store search results
Why “walled”: Apple Search Ads platform is the only buy. SKAdNetwork attribution replaces traditional measurement.
Cross-cut layers — vendors that touch every step
The Sankey above shows the SPATIAL flow — where the dollar moves. These three layers are different: they're services that observe or feed every step in the chain. Adding them to the chart would make it unreadable; naming them as a separate category teaches the full shape.
Identity & Data
touches 3 layersWhat: Resolves users across devices + sessions; supplies audience segments to bidders.
Where: Feeds into both buy-side (DSPs match audiences for targeting) and sell-side (SSPs enrich bid requests with first-party signals).
Verification & Brand Safety
touches 3 layersWhat: Pre-bid filtering (don't buy this URL) and post-bid measurement (was the ad actually viewable, was the page brand-safe, was the impression human?).
Where: Pre-bid: integrated into DSP bid logic. Post-bid: measures every served impression across the supply chain.
Attribution & Measurement
touches 3 layersWhat: Connects ad exposure to outcomes — purchases, app installs, store visits, brand lift. Multi-touch attribution, media-mix modeling, incrementality.
Where: Lives on the buy side. Pulls clean-room or hashed-ID data from DSPs + walled gardens + clickstream sources to attribute conversions back to specific ad placements.