Hi June,

Thank you for contacting Amplitude Support. Happy to help!
Jake here.

The difference usually would come from how amplitude merges user instance / user ID.
Following is detail of how we merge different users with different device/user ID.

- https://amplitude.com/docs/data/sources/instrument-track-unique-users

If you have more specifics on particular count difference and provide other reference data I can help you dig deeper into the issue!

I hope this helps, and please let me know if you have further questions.

Best regards,
Jake


P.S. Checkout upcoming events and user meetups on our events page.

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Hi Jake,

Thank you for your prompt response.

 

Based on the document you sent me, it seems that I have come to the following conclusion. Could you please confirm whether I have understood the whole process correctly?

(1) Unique User Count will be counted by User ID when an action (event) that has been acted has a User ID value linked to the device. (in other words, when the user is logged in on the device)

(2) But when an action has occurred and the device on which the action (event) happened does is not logged in (in other words, have no User ID data), Amplitude counts the user by its Amplitude ID

(3) Amplitude IDs are assigned based on Device IDs (when devices are not logged in), and Amplitude IDs may be merged based on the User ID that has been linked to the devices on which the Amplitude ID was assigned to. 

 

 

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Hi June,

You are on the right track but depending on the user behavior of setting user id [login/logout]

Amplitude merges the user under same user stream and they will be counted as a single user if they merge.
Please refer to the scenario in the document for the detail!

Best,
Jake


P.S. Checkout upcoming events and user meetups on our events page.

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