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User IDs are your own unique identifiers that you assign to individual users.
This guide explains how to send user IDs to Google Analytics, so you can connect
user behavior across different sessions, devices, and platforms.
Setting custom dimensions based on user IDs leads to dimensions with too many
unique values. Having too many unique values causes issues with Google
Analytics data and reporting accuracy. Learn more about best practices for
setting custom
dimensions.
Before you begin
Before you can send user IDs, make sure you've completed the following:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-05-23 UTC."],[[["User IDs, assigned by you, enable tracking user behavior across sessions, devices, and platforms in Google Analytics."],["To send user IDs to Google Analytics, ensure you have a Google Analytics account, a web data stream, and the Editor role or higher."],["Avoid setting custom dimensions based on user IDs and sending user IDs when a user isn't signed in to maintain data accuracy."],["Before implementing user IDs, review the best practices and guides linked in the document to avoid potential issues."]]],["User IDs are unique identifiers assigned to users to track their behavior across sessions, devices, and platforms within Google Analytics. To ensure data accuracy, avoid using user IDs for custom dimensions and only send them when users are signed in; do not set placeholder values. Before sending user IDs, establish a Google Analytics account and web data stream, and ensure the Editor role is assigned.\n"]]
