Generating Device ID for Client-Side and Server-Side Mixpanel

Hi event, Please stand by as I search the Mixpanel knowledge base for an AI-powered answer. I normally take about 15 seconds or so. In case AI cannot answer your question, feel free to reach out to Mixpanel support at mixpanel.com/get-support. If you have follow-up questions for this thread, please tag me again with your question: @kapa.ai <follow-up question> 👋

For Mixpanel, the way you generate and manage the device ID depends on whether you are using client-side or server-side tracking: ---

- Automatic Generation: Mixpanel’s client-side SDKs (JavaScript, Android, iOS, etc.) automatically generate a $device_id for each new user/session. This ID is local to the device and is persisted until you call .reset(), which will generate a new $device_id for the session. - No Manual Generation Needed: You do not need to manually generate or assign the $device_id when using Mixpanel’s client-side SDKs. The SDK handles this for you and attaches the $device_id to all events automatically. - Behavior: If you call .reset(), the SDK will clear the local storage and generate a new $device_id for the next session.> “Mixpanel’s SDKs will generate a $device_id and set that to distinct_id to associate these events to the same anonymous user.”

Identifying Users (Simplified) – Client-side Identity Management---

- Manual Generation Required: Mixpanel’s server-side SDKs and HTTP API do not generate IDs automatically. You are responsible for generating a unique device ID (commonly a UUID) and persisting it (e.g., in a cookie or session). - How to Generate: The recommended approach is to generate a UUID (universally unique identifier) and store it in a cookie or session variable for each user/session. - Usage: Set this value as the $device_id property in your event payloads. If you do not know the user’s identity (anonymous user), only set $device_id. When the user logs in, include both $device_id and $user_id in your events to allow Mixpanel to merge the identities.> “Mixpanel’s server-side SDKs and HTTP API do not generate IDs automatically, meaning your server is responsible for generating IDs and maintaining ID persistence.” Server-Side Best Practices – Identifying Users> “We recommend generating a UUID and storing that value in a cookie. All common server frameworks provide a simple way to set and retrieve cookies per request.” Identifying Users (Simplified) – Server-side Identity Management---**Summary Table:**| Environment | Who Generates $device_id? | How is it Generated? | |---------------|-----------------------------|-------------------------------------| | Client-side | Mixpanel SDK | Automatically, per device/session | | Server-side | You (the developer) | Generate UUID, store in cookie/etc. |If you need code examples or further details, let me know your specific environment (e.g., Python, Node.js, etc.)!

ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.