Client ID
01 Definition
Client ID meaning: An analytics identifier for a browser or device, usually stored in a cookie.
A client ID is a value Google Analytics assigns to identify a specific browser or device, commonly stored in a first-party cookie. It lets analytics group hits from the same device into users and sessions. Because it is per device and cookie-based, clearing cookies or switching devices creates a new client ID.
Also called
Why it matters
How Client ID fits the work
The client ID is the default way analytics stitches activity together, so understanding it explains why the same person can appear as several users across devices.
In context
A visitor browsing on a laptop and later on a phone generates two client IDs, so analytics counts two users unless a User ID links them.
Practical note
Client ID counts devices, not people, and consent choices or cookie deletion can reset it. For people-level analysis across devices, pair it with a User ID where you have one.