How do I get new users from the Amplitude API?

Call /api/2/users with m=new instead of m=active. Everything else about the request and the response shape is identical.

What counts as a new user in Amplitude?

Somebody whose first event Amplitude ever saw falls inside the window. That is usually the first page or screen they opened, not a signup, and it can be long before they created an account.

Why did my Amplitude new user count spike after a migration?

Probably an identity change. If how user_id is derived changes, every returning user looks brand new, and the spike is indistinguishable from a successful campaign.

Do anonymous visitors count as new users in Amplitude?

Yes. Amplitude creates a device id for a visitor with no user_id and that device is a user. Identity merging later ties the device to the account, taking the earlier first-seen date.

What should I read alongside Amplitude new users?

Active users. New rising while active stays flat means acquisition works and nothing sticks, which is the leakiest and most common shape. Neither number means much alone.

How to get new users from Amplitude

The call

The same endpoint as active users, with one letter changed.

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

m=new rather than m=active. Everything else is identical, including the response shape, which puts your numbers at data.series[0].

What new means

A user whose first event Amplitude ever saw falls inside the window.

Not somebody who signed up in the window. Not somebody who became a customer. First event, which is usually the first page they loaded or the first screen they opened, and which may be long before they created an account.

That makes it a top-of-funnel number. If you want signups, that is a specific event you instrumented and the segmentation endpoint counts it.

The thing that breaks the number

Amplitude decides "first ever" from the data it holds. Three situations make that misleading.

The day you added Amplitude. Every existing user you have is new on the day tracking went live. Your new user chart has a cliff at the start that is not a launch.

A backfill. Importing historical events moves users' first-seen dates backwards, which rewrites your new user history. Figures you reported last month change.

An identity change. If you alter how user_id is derived, every returning user looks brand new. A migration that changes id format produces a new-user spike indistinguishable from a successful campaign.

That last one is worth saying out loud before anybody celebrates.

Anonymous users count

Amplitude creates a device id for a visitor with no user_id, and that device is a user. So new users includes people who loaded one page and never came back.

Over time, identity merging ties a device to a user once they identify, and the first-seen date follows the earliest of the two. That is correct and it means a user's first-seen date can be earlier than their account creation date, which looks wrong on a join and is not.

New against active is the useful pair

Neither number means much alone.

New flat, active rising. Retention is improving. Existing users are coming back more.
New rising, active flat. Acquisition is working and nothing is sticking. The leakiest and most common shape.
Both rising together. Growth.
New rising, active falling. You are buying traffic that leaves faster than it arrives.

Place them side by side or the series tells you nothing you can act on.

Daily, weekly and monthly disagree

A weekly new-user figure is not the sum of seven daily ones, for the same de-duplication reason that applies to active users. Somebody whose first event is on Tuesday is new once in the week, and once on Tuesday.

In the new-user case the figures happen to be closer than they are for active users, because a person is only ever new once overall. They still are not equal, because the window boundary moves.

In the notch

Notch Metrics reports Amplitude new users as users first seen in the window, daily, weekly or monthly, bucketed in your Amplitude project's own timezone.

Place it beside active users and events and the three say which of the four shapes above you are in. Everything Amplitude reports, or download Notch Metrics.