> ## Documentation Index
> Fetch the complete documentation index at: https://docs.notifly.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# User property and event parameter keys

> Learn which key names Notifly supports and where keys containing periods are unavailable.

Keys for custom user properties and event parameters must match `^[A-Za-z][A-Za-z0-9_]*$`.

* Start with an uppercase or lowercase English letter (`A–Z` or `a–z`).
* After the first character, use only English letters, digits (`0–9`), or underscores (`_`).
* Spaces, Korean characters and other non-English letters, and special characters such as `.`, `$`, and `^` are prohibited.

For example, `delivery_address` and `productId2` are valid keys.

## Keys containing periods

Notifly still stores data sent with keys that fall outside this format, but some features may be unavailable. A user property with a period in its key, such as `delivery.address`, has these limitations.

* It does not appear in search results when you configure campaign conditions.
* It is hidden in **User List** and on user detail pages.
* It is omitted from CSV exports of all users.
* It is hidden in **Property management**, so you cannot configure encryption for it.


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