Event ID explained — the value that lets platforms recognize the same conversion across browser and server delivery for deduplication.
By The Ad Spend
Updated July 22, 2026.
An event ID is a value assigned to one conversion occurrence so systems can identify that action across delivery paths, retries and diagnostics.
Why it matters
Without an event-level identifier, a platform may not know that two records describe the same purchase or lead. Event IDs also let internal teams trace a platform event back to an order or lead without exposing personal data.
How it works across ad platforms
Platform or system
Current treatment
Meta
eventID in Pixel and event_id in CAPI for duplicate handling.
Pinterest
Shared event_id for tag/API copies.
Reddit
Current deduplication workflow requires a shared conversion identifier.
TikTok
Current Pixel/API duplicate handling uses platform-defined event identifiers.
Google Ads
Transaction ID serves a similar role for purchases.
Microsoft Advertising
Transaction IDs support offline/CAPI actions.
LinkedIn
Use current schema identifiers and duplicate rules.
Implementation rules
Use a non-sensitive stable ID.
One action gets one ID; a second action gets a second ID.
Reuse it on retries and duplicate delivery paths.
Do not include raw email or phone.
Store it in internal logs.
Common mistakes
Using timestamp alone.
Using a session ID for every action in the session.
Technically verified: July 22, 2026. This reference uses official platform sources only for platform-specific behavior. Definitions and implementation recommendations are editorial synthesis by The Ad Spend.
