Open source event tracking that runs inside your app.

Many events that matter happen on your server. Capture them there.

The browser only sees the click. Your server knows whether the upgrade actually went through. Track it where it happens, while keeping the visitor's context.

"use client";
import { track } from "@/lib/eventrail-client";
import { upgradePlan } from "./actions";

export function UpgradeButton() {
  return (
    <button
      onClick={() => {
        track("upgrade_plan_button_clicked", { plan: "pro" });
        upgradePlan("pro");
      }}
    >
      Upgrade to Pro
    </button>
  );
}

{
  name: "upgrade_plan_button_clicked",
  producerType: "remote",Came from the browser.
  location: "https://yourapp.com/pricing",
  sessionId: "8f3c…a1",
  consent: "accepted",
  producerProperties: { plan: "pro" },
  hubProperties: { userId: "usr_42", plan: "free" }
}

"use server";
import { track } from "@/lib/eventrail-server";
import { billing, errorCode } from "@/lib/billing"; // your code

export async function upgradePlan(plan: string) {
  // Called from the browser, runs on the server:
  try {
    await billing.upgrade(plan);
    track("plan_upgraded", { plan });
  } catch (err) {
    track("upgrade_plan_failed", { plan, reason: errorCode(err) });
    throw err;
  }
}

{
  name: "plan_upgraded",
  producerType: "local",Tracked on your server.
  location: "https://yourapp.com/pricing",
  sessionId: "8f3c…a1",
  consent: "accepted",
  producerProperties: { plan: "pro" },
  hubProperties: { userId: "usr_42", plan: "pro" }
}

{
  name: "upgrade_plan_failed",
  producerType: "local",
  location: "https://yourapp.com/pricing",
  sessionId: "8f3c…a1",
  consent: "accepted",
  producerProperties: { plan: "pro", reason: "card_declined" },
  hubProperties: { userId: "usr_42", plan: "free" }
}

Server events keep the visitor's session and consent. Browser events get the user your server knows. Same shape, same table.

• userId and plan come from your Hub's hubProperties(), which reads the signed-in user on every event. How to set it up
• Records are shortened. Each also has id, specVersion, producerName and three timestamps, and by default the Hub adds userAgent, forwardedFor and acceptLanguage to hubProperties.

Event data your data analyst actually enjoys working with.

• Strongly typed schema.Every row has the same typed, versioned columns (specVersion), with TypeScript types in the package. producerProperties and hubProperties are JSON you define.
• Understandable relations.Link events by sessionId, deduplicate on id, order on receivedAt. EventRecord reference →
• Raw but rich.No pre-aggregation, no sampling. Every row carries its context: location, consent, and whatever your server adds in hubProperties.

A daily funnel over the events above, in Postgres, using the table and snake_case columns the Postgres destination creates.

SELECT
  received_at::date AS day,
  COUNT(DISTINCT session_id) FILTER (
    WHERE name = 'page_view' AND location LIKE 'https://yourapp.com/pricing%'page_view is recorded by the TrackPageViews component; location is the page URL.
  ) AS viewed_pricing,
  COUNT(DISTINCT session_id) FILTER (
    WHERE name = 'upgrade_plan_button_clicked'
  ) AS clicked_upgrade,
  COUNT(DISTINCT session_id) FILTER (
    WHERE name = 'plan_upgraded' AND producer_type = 'local'
  ) AS upgraded,
  COUNT(DISTINCT session_id) FILTER (
    WHERE name = 'upgrade_plan_failed' AND producer_type = 'local'
  ) AS failed
FROM eventrail_events_v1
GROUP BY day
ORDER BY day;

There is nothing to host.

The Hub runs in your own server runtime. That's why it can read your session cookie and your auth, which a separate analytics service never can. No extra container, no dashboard to keep alive, no third-party origin to proxy.

Consent handling built in, not bolted on.

"use client";
import { createBrowserProducer } from "@eventrail/nextjs/client";

export const producer = createBrowserProducer({
  collectorLocation: "/api/eventrail",
  storeSessionId: "optIn", // or "enabled", "disabled", "optOut"
});

export const { track } = producer;

"use client";
import { producer } from "@/lib/eventrail-client";

export function ConsentBanner() {
  const consent = producer.useConsent();
  if (consent !== "unset") return null;

  return (
    <section aria-label="Cookie consent">
      <button onClick={() => producer.setConsent("accepted")}>Accept</button>
      <button onClick={() => producer.setConsent("denied")}>Decline</button>
    </section>
  );
}

When EventRail is the right choice

• Your app has a backend.Browser-only trackers see the click and guess the rest. EventRail records whether the upgrade actually went through, from the server that knows.
• You want the raw events in your own database.Not in a vendor's store behind an export API. Every row is yours to query with SQL, next to the rest of your data.
• You want every event tied to the signed-in user.A separate analytics service can't read your session or auth. The Hub runs inside your app, so it can.
• You want nothing extra to run.No self-hosted analytics stack, no extra container, no third-party origin to proxy. Just a package in your app.

See how EventRail compares →

Made in the Netherlands