Fast Flags
What are Fast Flags?
Fast Flags — usually called FFlags — are internal configuration variables that the Roblox engine reads when it starts. They control hundreds of behaviours that aren't exposed in any settings menu: frame-rate caps, renderer options, quality levels, experimental features and more.
Normally you'd have to hunt these values down in community spreadsheets and edit a JSON file by hand. BootStrap gives them a proper home: it stores your flags safely outside the game files and injects them into the launch command every time Roblox starts. Nothing is written into the game itself.
The Preset Manager
Open Settings → Fast Flags → Presets to browse BootStrap's built-in preset manager. Each entry is a safe, tested change with a plain-language description and sensible defaults — no flag knowledge required. Toggle a preset on, pick its options if it has any, and you're done.
Built-in presets reference
These are all of the presets that ship with BootStrap v1.0.0:
| Preset | Options | What it does |
|---|---|---|
| Manual fullscreen exit | Toggle | Lets you leave fullscreen manually instead of being dropped out automatically. |
| Disable DPI scaling | Toggle | Stops Roblox from applying DPI scaling, which can blur the image on high-resolution displays. |
| MSAA | 1x / 2x / 4x | Sets the level of multi-sample anti-aliasing for smoother edges. Higher values cost more performance. |
| Texture quality override | 0 – 3 | Forces a fixed texture resolution regardless of the automatic quality level (0 = lowest, 3 = highest). |
| FPS unlocker | Toggle | Lifts Roblox's 60 FPS cap by setting DFIntTaskSchedulerTargetFps=9999, letting the client render as fast as your hardware allows. |
| Disable shadows | Toggle | Removes dynamic shadows by setting FIntRenderShadowIntensity=0. A solid FPS gain on lower-end machines. |
| Disable post-processing | Toggle | Sets FFlagDisablePostFx=True, turning off bloom, blur and other full-screen effects. |
| Lighting technology | Voxel / ShadowMap / Future | Forces which lighting engine experiences use: Voxel and ShadowMap map to FFlagDebugForceFutureIsBrightPhase2, while Future maps to FFlagDebugForceFutureIsBrightPhase3. |
The lighting technology selector is especially popular: Future lighting looks dramatically better in supported experiences, while forcing Voxel can improve performance in heavy ones.
A word of caution
Only use flags you understand
Fast Flags are undocumented, internal variables. A wrong value can cause crashes, graphical glitches, broken gameplay — or get an experience to refuse to load. Stick to the built-in presets unless a flag comes from a source you trust, and never copy long flag lists from strangers "just because". If something breaks after adding a manual flag, remove it before reporting a problem.
The manual editor
If you need a flag that isn't covered by a preset, open Settings → Fast Flags → Manual editor. It's a simple JSON view where each key is a flag name and each value is what gets passed to the engine:
{
"DFIntTaskSchedulerTargetFps": 9999,
"FFlagDisablePostFx": "True",
"FIntRenderShadowIntensity": 0
}- Add a flag by typing a new key/value pair.
- Edit a flag by changing its value in place.
- Remove a flag by deleting its line.
Values are typed just like the engine expects them: numbers stay unquoted (9999), and enum-style values such as "True"/"False" are strings. The editor validates your JSON before saving, so a stray comma won't silently break your next launch.
Presets vs. manual entries
Preset toggles and manual editor entries are merged at launch. If both define the same flag, the manual editor wins — handy for temporarily overriding a preset without losing its configuration.
When flags are applied
Flags are read fresh every single launch and passed directly to the Roblox process. That means changes take effect the very next time you start a game — no reinstalling, no cache clearing — and disabling a flag restores stock behaviour instantly.
Resetting to defaults
To start over, use Settings → Fast Flags → Restore defaults. This clears every manual entry and switches off all presets in one go. Your mods, themes and other settings are untouched.