# Strict requirements for configuration filenames

> Source: https://docs.strapi.io/cms/migration/v4-to-v5/breaking-changes/strict-requirements-config-files

Strapi 5 enforces strict naming requirements for configuration files in the `/config/` folder: no case-insensitive duplicates, no duplicate base filenames, and certain reserved names are blocked; custom configurations should use files with names compliant to these rules.

Strapi 5 has strict requirements on the configuration filenames allowed to be loaded.

This page is part of the [breaking changes database](/cms/migration/v4-to-v5/breaking-changes) and provides information about the breaking change and additional instructions to migrate from Strapi v4 to Strapi 5.

- Is this breaking change affecting plugins? No
- Is this breaking change automatically handled by a codemod? No

## Breaking change description

**In Strapi v4**

Every `.js`, `.ts`, and `.json` file in the `/config/` folder of a Strapi project is loaded into `strapi.config`.

For example if there is a file called `/config/my-custom-config.js` it is loaded and accessible from `strapi.config.get('my-custom-config.someProperty')`.

**In Strapi 5**

Strapi 5 has strict requirements on the filenames allowed to be loaded (see notes for details).

## Migration

This section regroups useful notes and procedures about the introduced breaking change.

### Notes

In Strapi 5 filenames for configuration files should comply to these requirements:

- There should be no case-insensitive duplicate filenames. If both `CUSTOM.js` and `custom.js` exist, only one will be loaded.
- There should be no duplicate base filenames without extension. If both `custom.json` and `custom.js` exist, only one will be loaded.
- The following filenames are restricted and not loaded:
    - `uuid`
    - `hosting`
    - `license`
    - `enforce`
    - `disable`
    - `enable`
    - `plugin`
    - `strapi`
    - `middleware`
    - `telemetry`
    - `launchedAt`
    - `serveAdminPanel`
    - `autoReload`
    - `environment`
    - `packageJsonStrapi`
    - `info`
    - `autoReload`
- It is advised to use only alphanumeric characters (`a-zA-Z0-9`).
- All internal Strapi configurations (see the list of files in [configurations](/cms/configurations)) must conform to the known structure of those configuration files (i.e., no custom fields should be added to the existing files).

### Manual migration

Rename any of configuration files that are now invalid to a new name, and update the code to look in that path.

If you added custom fields to the internal Strapi configuration files, you should instead create a new file to store the custom configuration, and ensure the new filename matches the requirements for Strapi 5.