What is sesamy-go?

sesamy-go is a Go SDK for server-side tag management (SSTM) targeted at Google Analytics 4 (GA4). It gives you the building blocks to receive, transform, enrich, and forward GA4 tracking traffic on your own infrastructure instead of sending it directly from the browser to Google.

Why server-side?

Browser-side tracking has well-known problems:

• Ad-blockers and tracking-protection break event collection.
• First-party cookies set by third-party scripts are short-lived (Safari ITP, Chrome 3rd-party cookie deprecation).
• Sensitive parameters (IP, user-agent, user IDs, marketing identifiers) leak to vendor endpoints uncontrolled.
• You can't normalize, validate, redact, or enrich payloads before they hit GA.

Server-side tagging solves these by collecting events on a first-party endpoint under your domain. sesamy-go is the SDK to build that endpoint in Go.

What it does

• Receives GA4 traffic in either of the two protocols GA4 uses:
  • GTag — the form-encoded query-string protocol used by gtag.js. See reference/encoding.
  • Measurement Protocol v2 (MPv2) — JSON-based, used by SDK-style senders.
• Parses payloads into Go structs you can read, modify, and assert against.
• Converts between GTag ↔ MPv2 so middleware can be written once against MPv2 events even when traffic arrives as GTag.
• Enriches events with client ID, session ID, user ID, IP override, page location, engagement time, user-agent — via composable middleware.
• Forwards enriched events to a downstream tagging server (Server-side GTM, BigQuery sink, vendor endpoints) or directly to GA4.
• Ships server-side events to Grafana Loki for observability (integration/loki).
• Integrates with consent managers (Cookiebot) and marketing platforms (Emarsys, Tracify).

What it is not

• Not a hosted SaaS. You run it.
• Not a GTM replacement. It pairs with foomo/sesamy-cli, which generates the GTM container that points gtag.js at your sesamy-go endpoint.
• Not a generic web framework. It exposes http.Handler functions; bring your own router.

How it fits together

┌───────────┐     gtag.js / mpv2     ┌─────────────────┐    forwarded     ┌──────────────┐
│  browser  │ ──────────────────────▶│   sesamy-go     │ ────────────────▶│ GA4 / sGTM   │
└───────────┘  (your first-party     │   collect       │  enriched +      │ / BigQuery   │
               domain)               │   middleware    │  normalized      └──────────────┘
                                     └─────────────────┘
                                              │
                                              ▼
                                     ┌─────────────────┐
                                     │ Loki / logs /   │
                                     │ providers       │
                                     └─────────────────┘

Next: Getting started.