> For the complete documentation index, see [llms.txt](https://wiki.retrobat.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.retrobat.org/get-started/adding-bios-files.md).
# Adding BIOS files
Some emulators require BIOS files to work correctly.
{% hint style="warning" %}
BIOS files are copyrighted and are therefore not included with RetroBat. The team cannot legally distribute them: you need to dump them from your own original hardware.
{% endhint %}
## Location
As a general rule, BIOS files must be copied to the `bios` folder of RetroBat, for example `C:\RetroBat\bios\`.
{% hint style="info" %}
* File names must match **exactly** the names expected by RetroBat (e.g. `scph5501.bin`). Do not rename them.
* Some systems need their BIOS files in a subfolder or in another location. This is specified on each system's page in the [Supported Game Systems](/systems-and-emulators/supported-game-systems.md) section, along with the list of required BIOS files.
{% endhint %}
## Missing BIOS check
RetroBat can check your BIOS files: open the [MAIN MENU](/navigation/main-menu.md), go to [GAME SETTINGS](/navigation/main-menu.md#game-settings), then select **MISSING BIOS CHECK** in the **BIOS SETTINGS** group.
The result lists, for each system, the BIOS files that need your attention:
* **Missing**  : the file was not found.
* **Invalid**  : the file is present, but its checksum (MD5) does not match any known version. It may still work: test the system to make sure.
{% hint style="info" %}
By default, RetroBat also checks the BIOS files when you start a game. If a BIOS file is missing for the system, a warning is displayed and you can choose to launch the game anyway.
This check can be disabled with the **CHECK BIOS FILES BEFORE RUNNING A GAME** option, in the same **BIOS SETTINGS** group.
{% endhint %}
---
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