> For the complete documentation index, see [llms.txt](https://help.littledata.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.littledata.io/event-editor/event-customiser-faq.md).

# Event Editor FAQ and troubleshooting

Use this page to answer common questions and troubleshoot Event Editor issues.

## General

* **Do changes affect historical data?**\
  No. Only future events use the new configuration.
* **What happens if a field path has a typo?**\
  Littledata skips that mapping for that event. The event still sends.
* **Can I customise client-side events?**\
  Support is limited and depends on the destination.
* **Can I create multiple customisations for one event?**\
  Yes. They run in this order: Filter, Modify, then Clone.
* **Is there a limit on custom parameters?**\
  Yes. Limits vary by destination. The button disables at the limit.

## Field mappings

* **What is a locked mapping?**\
  It uses a fixed source and destination. You cannot edit or remove it.
* **Can I remove a standard mapping?**\
  Usually no. You can override the source, but not remove the mapping.
* **Why is my source field empty in the preview?**\
  The path may be wrong. The sample event may be old. The field may be conditional.
* **How do I use a static value?**\
  Choose **Static value** in the source dropdown, then enter the value.


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