Which Amplitude endpoint returns event counts?

/api/2/events/segmentation, with an e parameter holding a URL-encoded JSON object. The users endpoint answers active and new users and does not count events.

What does event_type _active mean in Amplitude?

Any event, of any type. It is one of two reserved types, alongside _new, which matches a user's first event. For a specific event, pass its name instead.

Why does my Amplitude segmentation call return a 400?

Usually the e parameter is not URL encoded. It is JSON inside a query string, so braces and quotes must be escaped. Use URLSearchParams rather than building the string by hand.

What is the difference between totals and uniques in Amplitude?

totals counts every event with repeats included. uniques counts distinct users who fired it. People often reach for totals to answer how many people did something, which uniques is the right metric for.

Is Amplitude event volume a good product metric?

It is a better billing signal than a product one, because Amplitude meters on event volume. A component that starts firing twice doubles the number with nobody new arriving, so place active users beside it.

How to count events in Amplitude by API

The endpoint

Event counts come from /api/2/events/segmentation, not from the users endpoint.

curl -s -u "$API_KEY:$SECRET_KEY" \
  'https://amplitude.com/api/2/events/segmentation?e=%7B%22event_type%22%3A%22_active%22%7D&start=20261001&end=20261007&i=1&m=totals'

That e parameter is a JSON object, URL encoded. Decoded it is:

{ "event_type": "_active" }

The special event types

Amplitude reserves two event types that are not events you sent.

`event_type`	What it means
`_active`	Any event, of any type
`_new`	A user's first event

_active is what you want for total volume. For one specific event, use its name:

{ "event_type": "subscription_created" }

Encoding the e parameter

This is where most of the pain is. e is JSON in a query string, so it must be encoded, and an unencoded brace will either 400 or silently mangle.

const url = new URL("https://amplitude.com/api/2/events/segmentation");
url.searchParams.set("e", JSON.stringify({ event_type: "_active" }));
url.searchParams.set("start", "20261001");
url.searchParams.set("end", "20261007");
url.searchParams.set("i", "1");
url.searchParams.set("m", "totals");

URLSearchParams encodes for you. Building the string by hand is how the quotes get lost.

m decides totals against uniques

`m`	What you get
`totals`	Every event, repeats counted
`uniques`	Distinct users who fired it
`avg`	Average per active user

totals for volume. uniques for "how many people did this", which is a different and usually more useful question, and the one people reach for totals by mistake to answer.

Filtering on a property

{
  "event_type": "subscription_created",
  "filters": [
    {
      "subprop_type": "event",
      "subprop_key": "plan",
      "subprop_op": "is",
      "subprop_value": ["annual"]
    }
  ]
}

subprop_value is an array even for one value. A string there is a quiet no-match rather than an error, so a filtered figure that returns zero is worth checking against the unfiltered one before you believe it.

What a raw event count is good for

Amplitude bills on event volume, so this number is close to a live view of next month's invoice. That is the use case where it is unambiguous.

As a product signal it is weak. A single component that starts firing twice doubles your volume with nobody new arriving, and a tracking change looks identical to a usage change in this series.

Put active users beside it. Events climbing while active users hold flat means you shipped more instrumentation. Both climbing together means something actually happened.

No autocapture, which helps

Unlike some product analytics tools, Amplitude does not autocapture by default. Every event in that total is one your instrumentation deliberately sent.

That makes the figure a cleaner product signal than an autocaptured one, and a less useful proxy for user activity, because anything you forgot to instrument is invisible rather than approximated.

In the notch

Notch Metrics reports Amplitude events as every event recorded in the window, of every type, bucketed daily, weekly or monthly in your project's own timezone, with a sparkline and a comparison against the previous window.

Everything Amplitude reports, or download Notch Metrics.

How to count events in Amplitude by API

Questions