Using the top navigation bar, click the feature ‘User Look-Up.’ This is where you can get a live stream of events tracked in the last 24h.
Select a specific user, and you’ll see the user profile, user ID, amplitude ID, and all the device IDs that Amplitude has seen, including other information (i.e.: demographics, SDKs, when we first saw the user, live event stream, etc.)
If you see a User ID, it's because it has already been set. If the value is null, the User ID has not been set.
There’s also a raw version that you can access for debugging purposes by toggling to ‘Raw.
Best practices for setting user IDs are available in our Help Center under identify your users, along with instructions to look up event data for individual users.