How to query active users from the Amplitude Dashboard REST API

Which Amplitude API answers this?

The Dashboard REST API, which is the read-only one. Amplitude also has an HTTP API for sending events and an Export API for raw data, and neither answers "how many active users last week".

curl -s -u "$API_KEY:$SECRET_KEY" \
  'https://amplitude.com/api/2/users?start=20261001&end=20261007&m=active&i=1'

Basic auth with two keys

Not a bearer token. The API key is the username and the secret key is the password, in HTTP Basic auth.

const auth = Buffer.from(`${apiKey}:${secretKey}`).toString("base64");
const res = await fetch(url, { headers: { Authorization: `Basic ${auth}` } });

Both come from project settings and both are project-scoped. The secret key is a secret in the real sense: it reads every event in the project, so it belongs on a server and never in a client.

The regional host

A US key pair against the EU host fails to authenticate, and the message reads like a revoked key. People regenerate credentials over this. Check the host first.

The m parameter decides what you get

/api/2/users returns active or new users depending on one letter.

Everything else about the call is identical, which is convenient and means a single character typo changes your metric without changing your code shape.

Dates and intervals

start and end are YYYYMMDD with no separators. Not ISO, not a timestamp. 20261001.

i is the interval: 1 for daily, 7 for weekly, 30 for monthly. There is no hourly option, so anything finer than a day is not available from this endpoint at all.

The response shape

{
  "data": {
    "series": [[120, 98, 143, 131, 110, 76, 89]],
    "seriesLabels": [0],
    "xValues": ["2026-10-01", "2026-10-02", "..."]
  }
}

series is an array of series, and with no segmentation there is exactly one, so the numbers you want are at data.series[0]. xValues holds the matching dates.

Reading data.series as the array of numbers rather than as the array of series is the mistake everybody makes once, and it fails with a type error rather than a wrong number, which is the kind way round.

De-duplication

The daily series de-duplicates within each day. A weekly figure, asked for with i=7, de-duplicates across the week.

So summing seven daily values does not give you the weekly value. It gives you something larger, inflated by exactly how much your users come back, which is the retention you were presumably trying to measure separately.

If you want both, ask twice.

Event counts use a different endpoint

Active users come from /api/2/users. Event volume comes from /api/2/events/segmentation, with its own parameters and the same response shape. Two endpoints, one shape, which makes a shared parser worth writing.

Or read it off the notch

Notch Metrics calls this endpoint and reports Amplitude active users, new users and events in the MacBook notch, daily, weekly or monthly, bucketed in your Amplitude project's own timezone.

Both keys are encrypted on the server and neither reaches your Mac. Everything Amplitude reports, or download Notch Metrics.