Three terms get used interchangeably in attribution conversations: webhook, postback, and server-to-server. They overlap enough that the confusion is understandable, and they differ enough that picking the wrong one sends data to the wrong place. A growth team that conflates them ends up either missing optimization signal on their ad platforms or missing events in their own warehouse.
This guide draws the line cleanly: what each mechanism is, which direction the data flows, who consumes it, and when to reach for which.
A webhook delivers a full event payload from your MMP to an endpoint you control; a postback sends a conversion signal from your MMP to an ad network so it can optimize; and a server-to-server (S2S) event is sent from your backend to your MMP to record an event the SDK did not capture. The first two are outbound from the MMP, the third is inbound to it.
The three mechanisms at a glance
| Webhook | Postback | Server-to-server (S2S) | |
|---|---|---|---|
| Direction | MMP to your systems | MMP to ad network | Your backend to MMP |
| Primary consumer | Your warehouse, CRM, internal services | Ad platform optimization engine | Your MMP attribution |
| Payload | Full event detail you define | Conversion signal mapped to the network spec | Event you are reporting (purchase, signup) |
| Latency | Real time | Near real time | Real time |
| Typical use | Pipe every event to your stack | Feed quality signals back to Meta, Google, TikTok | Record server-side events with no client SDK |
Webhooks: events to systems you own
A webhook is a real-time HTTP POST from your MMP to a URL you control, carrying the complete event payload. You decide what it triggers: a warehouse insert, a lifecycle journey, a Slack alert, a fraud check.
Reach for a webhook when the consumer is your own infrastructure and you want the full event, not just a conversion flag. It is the backbone of getting attribution data out of the dashboard and into the tools that act on it. The step-by-step is in how to send mobile attribution events to webhooks.
A practical note worth checking before you design around webhooks: whether they are included on your MMP plan. Some vendors gate real-time webhook delivery to higher tiers, which is the subject of Branch webhooks: what they cost and the free alternative.
Postbacks: signals back to ad networks
A postback sends a conversion signal from your MMP back to the ad network that drove the user, so the network's optimization engine can learn. When you tell Meta or Google that an install became a paying user, their algorithm bids toward more users like that one.
Reach for a postback when the goal is campaign optimization, not internal data movement. The payload is shaped to the network's spec, and the value is in the loop it closes: better signal in, better targeting out. Linkrunner sends quality-user and revenue postbacks to networks like Meta, Google, and TikTok, covered on the Google and Meta ads measurement page.
Postbacks are also where iOS gets specific. Under SKAdNetwork, the postback is privacy-preserving and sent by Apple, which changes the timing and granularity of the signal compared to an Android postback.
Server-to-server: events from your backend to the MMP
S2S runs the other direction. Your own server sends an event to the MMP, usually because the event happens where the client SDK cannot see it: a renewal billed on your backend, a purchase confirmed by a payment webhook, a fraud reversal.
Reach for S2S when the source of truth for an event is your server, not the device. It keeps attribution complete for events the SDK would otherwise miss, and it is how backend-confirmed revenue gets attributed to the right campaign.
How they work together
In a healthy setup, all three run at once, each doing its job:
- The SDK and your S2S events feed the MMP a complete picture of what users do.
- The MMP fires postbacks to ad networks so campaigns optimize on real outcomes.
- The MMP fires webhooks to your warehouse, CRM, and services so your own teams act on the same events in real time.
Get the direction right and the data lands where it belongs. Get it wrong and you either starve your ad platforms of signal or starve your warehouse of events.
FAQ
Q: Is a webhook the same as a postback?
No. Both are outbound from your MMP, but a webhook delivers a full event payload to a system you own, while a postback sends a conversion signal to an ad network for optimization. Different consumer, different payload, different purpose.
Q: When should I use server-to-server instead of a webhook?
Use S2S when you are sending an event into your MMP from your backend, typically an event the client SDK cannot observe, such as a renewal or a backend-confirmed purchase. Use a webhook when you are receiving events out of the MMP into your own systems.
Q: Do I need all three?
Most teams running paid acquisition do. S2S keeps attribution complete, postbacks optimize campaigns, and webhooks move events into your stack. They are complementary, not alternatives.
Q: Are postbacks real time?
Android postbacks are near real time. iOS postbacks under SKAdNetwork are sent by Apple on a privacy-preserving schedule, so they arrive later and with less granularity by design.
Q: Does webhook availability depend on my plan?
With some MMPs, yes. Real-time webhook delivery can be reserved for higher tiers. Linkrunner includes webhooks on every plan, which you can confirm on the pricing page.
Closing
The simplest way to keep these straight: webhooks push full events to systems you own, postbacks push conversion signals to ad networks, and S2S pushes backend events into your MMP. Once the direction and the consumer are clear, choosing the right one stops being a guessing game.
If you want all three working without gating real-time delivery behind a tier, start with Linkrunner free or read the docs.