---
title: About the SYS Field Name Prefix
slug: '1567'
canonical_url: https://docs.coveo.com/en/1567/
collection: index-content
source_format: adoc
---
# About the SYS Field Name Prefix
While [inspecting items with the Content Browser](https://docs.coveo.com/en/2053/), you might have noticed some field names with the prefix `sys`.
These fields may appear redundant, since their value is identical to the value of fields with the same name, minus the `sys` prefix.

**Examples**

* `date` and `sysdate`
* `filetype` and `sysfiletype`
* `size` and `syssize`

These field pairs coexist for compatibility reasons.
In previous versions of Coveo, the names of the system fields were prefixed with `sys`.
This prefix was abandoned in the cloud version of Coveo.
However, for backward compatibility reasons the Coveo [REST Search API](https://docs.coveo.com/en/52/) still includes the older field names.

> **Important**
>
> In a future version of the Search API, fields prefixed with `sys` won't be available anymore.
> To future-proof your Coveo-powered search pages, ensure they no longer use fields with the `sys` prefix.