Hi @richard , 

This is Nehita from the  Amplitude Support team, thanks for writing into the Community! 

To answer your question, once an event is sent in, it can’t be edited. However, you can add the user ID to the new events but not to the past events. It’s important to remember that Amplitude is an events-based platform, and so any events we ingest are ingested with the user and event properties at the time they occurred. Our event data is historical and immutable and cannot be changed once ingested. So when you query on some Event A where some_property=X, we are looking for the users who have triggered Event A and some_property was equal to X at the time the event occurred. 

I hope this is helpful, but please let me know if you have any follow-up questions!

Best,

Nehita 

Hi @Nehita I. ,
Thanks for your reply. I know the event created can’t be edited so what I want to achieve is to help Amplitude system know this anonymous user is “user F560”. By that, you can merge the anonymous user with “user F560” just like what you did when an anonymous user log in. Is that achievable?

In my opinion, maybe we could send an API request to let you know this anonymous user’s actual user_id and you can help merge the anonymous user and “user F560”.

Thanks!

Hi @richard, Thanks for following up here. I’m Jeremie the community manager. I ran a search in the community and found this thread on merging uses. Please keep us posted if you find anything else as you work out the next steps.