Why did my user count jump in Amplitude?
The Amplitude help pages give 3 common reasons. The first to rule out: A person who clears cookies or browses privately can get a new device ID, as Amplitude's docs explain, so the same person can show up as a new user.
What causes it?
A person who clears cookies or browses privately can get a new device ID, as Amplitude's docs explain, so the same person can show up as a new user.
In the Amplitude help:
The device ID persists unless a user clears browser cookies or browses in private mode.
Track unique users | Amplitude Docs, read 2026-11-12.If an existing customer is given a new user ID, Amplitude counts them as another unique user, so a change in how IDs are made can lift the count.
In the Amplitude help:
If you create a new user ID for an existing user, Amplitude recognizes them as different unique users.
Track unique users | Amplitude Docs, read 2026-11-12.Two different user IDs for one person stay as two users, since Amplitude does not merge user IDs.
In the Amplitude help:
Amplitude can't merge user IDs.
Track unique users | Amplitude Docs, read 2026-11-12.
How do I check it myself?
Check with whoever set up your tracking that each person keeps one stable user ID over time.
In the Amplitude help:
Use a stable value for the user ID.
Track unique users | Amplitude Docs, read 2026-11-12.Check that people who have not signed in are not given a user ID of their own, which Amplitude's docs advise against.
In the Amplitude help:
Don't assign anonymous users a user ID.
Track unique users | Amplitude Docs, read 2026-11-12.
How does Amplitude work with Feder?
- Connect Amplitude to Feder and it joins your Visits apps.
- When you connect Amplitude, Feder checks the connection straight away and shows Connected only when that check passes. If a reading cannot be taken later, Feder shows it as not read, never as zero.
Some numbers are too quiet to judge daily, such as a form filled in a few times a week. Until there is enough of your own history to judge a change, Feder says it is still learning and scores nothing, rather than guessing.
See whether you can trust the numbers in Amplitude, one of your Visits apps. Feder only reads. It never changes anything in Amplitude.
What else goes wrong with these numbers?
- Why did my session count drop in Amplitude?Amplitude
- Why did my user count drop in Amplitude?Amplitude
- Why did Google Analytics stop collecting data?Google Analytics
- Why aren't my key events showing in Google Analytics?Google Analytics
- Why does Google Analytics show (not set)?Google Analytics
See every question.
Where do these answers come from?
Every cause and check on this page comes from the Amplitude help pages, quoted above with the date we read them. Last reviewed 2026-11-12. We read them again by 2027-11-12. If one changes, this page changes or comes down.