What Fast Flags Do in Bloxstrap
Fast Flags are command-line settings that change how Roblox runs on your computer when you launch it through Bloxstrap. They let you adjust graphics quality, enable experimental features, turn off animations, or speed up load times — all without touching Roblox's official settings. Fast Flags are stored in a single file that Bloxstrap reads every time you start the game.
Bloxstrap is a third-party launcher for Roblox that sits between you and the official client. When you add a Fast Flag, you're telling Bloxstrap to pass that instruction to Roblox before it fully loads. This means the flag takes effect when ready, without waiting for Roblox to update or without needing to change anything inside the game itself.
Common reasons to use Fast Flags include reducing lag on older computers, enabling higher graphics settings on newer ones, disabling motion blur or camera shake, or testing features that Roblox hasn't released to everyone yet. The flags themselves are harmless — they're just settings, the same way you'd adjust brightness or sound volume.
Key Takeaways
- Fast Flags are stored in a single text file called ClientAppSettings.json that lives in your Bloxstrap folder, not in Roblox itself.
- You edit the file by opening it in Notepad or any text editor, adding the flag in the correct format, and saving it before launching Bloxstrap.
- The most common flags control graphics (DFIntTargetMegabytesMem), animations (DFFlagDisableMotionBlur), and performance (DFIntTaskSchedulerTargetFps).
- If a flag breaks something or causes crashes, you can delete it from the file and the game will return to normal on your next launch.
- Fast Flags only work in Bloxstrap — they have no effect if you launch Roblox through the official client or through a web browser.
Finding Your Bloxstrap Folder and the Fast Flags File
Bloxstrap stores all its files in a folder on your computer. The location depends on your Windows version, but the easiest way to find it is to open Bloxstrap itself, click the three-line menu icon in the top right, and select "Open Bloxstrap folder". A Windows Explorer window will open showing you the exact location.
Inside that folder, look for a file called ClientAppSettings.json. If it does not exist yet, you will create it in the next step. If it does exist, right-click it and choose "Open with" and then select Notepad (or Notepad++, VS Code, or any text editor you have). Do not use Microsoft Word — it adds formatting that will break the file.
The file path is usually something like C:\Users\[YourUsername]\AppData\Local\Bloxstrap\, but Bloxstrap's menu shortcut is faster than hunting for it manually. Once you have the file open in a text editor, you are ready to add flags.
The Correct Format for Adding a Fast Flag
Fast Flags follow a strict format. If the format is wrong, Bloxstrap will ignore the flag or the game will crash. The format looks like this:
{"FlagName": value}
The flag name always starts with a prefix that tells Roblox what type of setting it is. DFInt means an integer (a whole number). DFFlag means a true-or-false toggle. DFString means text. For example:
- {"DFIntTaskSchedulerTargetFps": 60} — sets the frame rate to 60 (a number, so DFInt)
- {"DFFlagDisableMotionBlur": true} — turns off motion blur (true or false, so DFFlag)
- {"DFStringCrashReporterUrl": ""} — sets a text value to empty (text, so DFString)
If your ClientAppSettings.json file is empty or does not exist, start with an opening curly brace {, add your flags, and close with }. If the file already has flags in it, add your new flag inside the curly braces, separated from other flags by a comma. Save the file, close it, and launch Bloxstrap — the flag will take effect on the next game start.
Common Fast Flags and What They Do
These flags are widely used and unlikely to cause problems. Each one is a real setting that Roblox recognizes. Always add them one at a time and test the game after each addition, so you know which flag caused a problem if something breaks.
| Flag Name | What It Does | Example Value |
|---|---|---|
| DFIntTaskSchedulerTargetFps | Sets your target frame rate (frames per second) | 60, 120, or 240 |
| DFFlagDisableMotionBlur | Turns off motion blur effect | true |
| DFFlagDisableCameraShake | Disables camera shake in games | true |
| DFIntTargetMegabytesMem | Limits how much memory Roblox uses | 512, 1024, or 2048 |
| DFFlagDebugRenderFPS | Shows your frame rate in the top-left corner | true |
| DFIntRenderGLRenderThreads | Number of threads for graphics rendering | 1, 2, or 4 |
For a computer with 4 GB of RAM or less, setting DFIntTargetMegabytesMem to 512 can reduce stuttering. For a newer computer with a good graphics card, increasing DFIntTaskSchedulerTargetFps to 120 or 240 can make the game feel smoother. Start with one flag, launch a game, and see if it helps or hurts performance before adding more.
Testing Your Flags and Fixing Problems
After you add a flag and save the file, close Bloxstrap completely and reopen it. Launch any Roblox game and play for a few minutes to see if the flag works as intended. If the game crashes, freezes, or runs worse, the flag is the problem.
To remove a flag, open ClientAppSettings.json again in your text editor, delete the line with that flag, and save the file. If you have multiple flags and one is causing trouble, delete them one at a time and test after each deletion so you find the culprit. Once you delete a flag, the game returns to normal on your next launch — there is no permanent damage.
If you want to start completely fresh, you can delete the entire ClientAppSettings.json file. Bloxstrap will create a new empty one the next time you launch, and Roblox will run with no custom flags. This is a safe way to reset if you have added too many flags and cannot figure out which one is causing problems.
Why Some Flags Stop Working After Roblox Updates
Roblox updates regularly, and sometimes those updates change how flags work or remove old ones entirely. A flag that worked last month might do nothing this month, or it might cause a crash if Roblox changed the underlying code. This is normal and not a sign that you did something wrong.
When a flag stops working, the safest move is to delete it from your ClientAppSettings.json file and look for a newer flag that does the same thing. Roblox community forums and Bloxstrap documentation often list which flags are currently active. If you are not sure whether a flag is still valid, remove it and test — if the game runs fine without it, you have your answer.
Never add flags you do not understand or that come from untrusted sources. Flags are just settings, but a malformed flag or one designed to break the game can cause crashes. Stick to flags from official Roblox documentation, Bloxstrap's own guides, or well-known community sources.
Frequently Asked Questions
Will using Fast Flags get me banned from Roblox?
No. Fast Flags are settings that change how the client runs locally on your computer. Roblox does not detect or punish players for using them. They are not cheats or exploits — they are the same settings that Roblox developers use internally to test the game.
Can I use Fast Flags if I play Roblox in a web browser?
No. Fast Flags only work in Bloxstrap. If you launch Roblox through a web browser or through the official Roblox client, the flags have no effect. You must use Bloxstrap as your launcher for the flags to work.
What happens if I add a flag with the wrong format?
Bloxstrap will either ignore the flag or the game will crash on startup. If it crashes, delete the malformed flag from ClientAppSettings.json, save the file, and try again. Check that you have the correct prefix (DFInt, DFFlag, or DFString), that numbers are not in quotes, and that true and false are lowercase.
Can I add flags to improve my frame rate on a low-end computer?
Yes. Setting DFIntTaskSchedulerTargetFps to a lower number like 30 or 60, and DFIntTargetMegabytesMem to 512 or 256, can help. You can also disable visual effects like motion blur and camera shake. However, no flag will make a very old computer run demanding games smoothly — flags optimize, they do not create performance from nothing.
Where do I find new Fast Flags to try?
The Bloxstrap GitHub page and community forums list flags that are currently working. Roblox also publishes some flags in their official documentation. Always test a new flag in a straightforward game first before using it in a game you care about, and add only one flag at a time so you know which one caused a problem if something breaks.