What is an advertiser?

What an advertiser buys

Attention, in a context, with some probability of the right person seeing it. Everything else in the industry — targeting, formats, measurement, ad tech — exists to make that transaction more precise.

The distinction from a publisher is simply which side of the transaction you are on. Many businesses are both: a large app both buys users and sells inventory.

The decisions that matter

• What outcome counts — see conversion. This determines what every optimisation system pursues.
• What it is worth, which requires LTV and a payback horizon.
• Where to buy, which is a reach and quality decision rather than only a price one.
• How to measure, which determines whether the other three decisions are informed or guessed.
• What not to appear beside, which is brand safety and is easier to set before a problem than after.

What changed for advertisers

Three things simultaneously, over roughly five years. Identifier loss removed the targeting and measurement precision the discipline was built on. Platform consolidation moved more spend into walled gardens where the platform measures itself. And a new surface appeared — AI media — whose economics do not resemble the channels a media plan is normally built from.

The common thread is that the advertiser's own measurement matters more than it did. When platform numbers were verifiable and identifiers made attribution reliable, an advertiser could reasonably outsource the question of what worked. Now the only reliable read is the one you produce yourself, which is why incrementality capability has gone from sophistication to baseline.