> ## Documentation Index
> Fetch the complete documentation index at: https://docsuncv2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# setfflag

Writes a new value to a Roblox Fast Flag.

```luau theme={null}
setfflag(name: string, value: string): ()
```

Pass the flag's literal name, without a prefix (e.g. `"EnablePreloading"`, not `"DFFlagEnablePreloading"`).

Flag names follow one of six type prefixes: `FFlag` / `DFFlag` (booleans), `FInt` / `DFInt` (integers), `FString` / `DFString` (strings). The leading `D` marks dynamic flags, which refresh at runtime; the rest lock at session start.

`value` is always passed as a string, regardless of the flag's declared type.

## Parameters

| Parameter | Type     | Description                                     |
| --------- | -------- | ----------------------------------------------- |
| `name`    | `string` | Flag name.                                      |
| `value`   | `string` | E.g. `"60"` for an FInt, `"true"` for an FFlag. |

## Returns

<code title="the function does not return a value.">void</code>

## Example

<CodeGroup>
  ```luau Example 1 theme={null}
  <<<<<<< HEAD
  setfflag("test", "test")
  =======
  -- setfflag(name: string, value: string): ()
  >>>>>>> 50e30f53759b0538759af25c9b271514aa2c9290
  ```

  ```luau Example 2 theme={null}
  setfflag("EnablePreloading", "false") -- disables Roblox's asset preloading
  ```
</CodeGroup>

<Tip>
  FFlags modify core client behaviors and graphics engine properties.
</Tip>