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Custom stack - Postscript

Send every Custom stack event to Postscript, server-side

Q: How do I check that Custom stack events are reaching Postscript?

Open Postscript › Subscribers › the individual subscriber's activity feed.

Q: Can one purchase trigger the same flow twice?

No. One order produces one event, so a single purchase cannot trigger the same flow twice.

Each event is resolved to a person against a 750M+ device graph before it reaches Postscript, so flows trigger on a known profile rather than an anonymous session.

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US device IDs in the graph: 750M+
Match rate on events: 90%+
Identity window, per customer: Lifetime
Most brands are live: <20 min

How it flows

How a Custom stack event reaches Postscript. Captured on the server, resolved to a person, then sent.

01 Capture

Captured from Custom stack

Not on the list? Send events to Upstack from any stack over webhook or direct post, with the same schema and the same resolution.

See the Custom stack integration

Custom stackWhat it sends

event_namewhatever you choose to call it
user identifiersany of email, phone, external ID
value / currencyif the event carries revenue
custom propertiesany attribute in your own schema

02 Understand

Resolved to one person before it leaves

Every Custom stack event is matched against a 750M+ device graph, so a phone browse and a desktop checkout resolve to one customer rather than two strangers.

How resolution works

Resolved before it is sent

IdentityMatched against a 750M+ device graph, so a phone browse and a desktop checkout resolve to one customer.
customer_typeNew or returning, resolved before send.
DeduplicationOne order produces one event, so a single purchase cannot trigger the same flow twice.
Bot and fraud filteringAutomated traffic never becomes a profile, so list quality and deliverability are not paying for it.

Messaging mistakes are expensive and public. These controls exist so a flow never fires against a profile that should not have received it.

03 Activate

Delivered to Postscript

Send identity-resolved events to Postscript so SMS flows reach subscribers the pixel missed.

See the Postscript integration

PostscriptWhat it receives

phonesubscriber key
emailprofile matching
order / cart propertiesautomation triggers

The catch

Custom schemas tend to carry identifiers in whatever field made sense at the time.

The profile key has to be normalized before it reaches a messaging tool or nothing matches.

Where to check in PostscriptSending you can audit

Postscript Subscribers the individual subscriber's activity feed

What changes

What changes when Custom stack feeds Postscript. Two gains on the Postscript side, two on the Custom stack side.

Postscript

Server-side delivery

Events reach Postscript through its server API rather than the browser, so ad blockers and ITP don’t cost you conversions.

Postscript

Identity-resolved events

Events sent to Postscript carry the resolved customer whenever Upstack can identify one, matched against a 750M+ device graph.

Custom stack

Any stack, any framework

Headless, custom checkout, native app or a platform we haven’t listed: if it can make an HTTP request, it can send to Upstack.

Custom stack

The same event schema

Custom events are resolved, filtered and forwarded exactly like a Shopify order.

Setup

Post directly from your backend so nothing depends on the browser.

Connect Custom stack once and every destination, Postscript included, is forwarded the same resolved events.

Upstack dashboardExample

Custom stack Data source Connected

Postscript Destination Healthy

Read the full Postscript setup guide

01

Connect Custom stack

Not on the list? Send events to Upstack from any stack over webhook or direct post, with the same schema and the same resolution.
02

Add the Postscript destination

Under Destinations, add Postscript. Every resolved Custom stack event is then forwarded to it.
03

Check delivery to Postscript

Trace any event to the profile it resolved to, and see why.