What Fast Flags Do and Where to Find Them

Fast Flags are command-line arguments that change how Roblox runs when you launch it through Bloxstrap. They let you adjust graphics settings, enable experimental features, reduce lag, or unlock performance tweaks that the standard Roblox launcher doesn't expose in its menus. Fast Flags are stored as text in a configuration file that Bloxstrap reads each time you start the game.

Bloxstrap pulls Fast Flags from a file called ClientSettings.json, which sits in your Bloxstrap data folder. You edit this file directly by adding or changing lines of code. The flags themselves come from Roblox's internal development settings — they're the same toggles Roblox engineers use to test features before release.

Common reasons players add Fast Flags include lowering graphics to improve frame rate, enabling a frame rate counter, turning off motion blur, or testing features that Roblox hasn't rolled out to everyone yet. Some flags reduce stuttering or memory use on older computers.

Key Takeaways

  • Fast Flags are stored in a file called ClientSettings.json inside your Bloxstrap folder, which you edit as plain text.
  • You can find the Bloxstrap data folder by opening Bloxstrap, going to Settings, and clicking "Open data folder" — this shows you exactly where to look.
  • Each Fast Flag is a single line of code in JSON format, and a single typo or missing comma will prevent Bloxstrap from reading the file.
  • After you add or change a Fast Flag, save the file and restart Bloxstrap completely — the changes take effect only on the next launch.
  • If Bloxstrap stops launching after you edit ClientSettings.json, the file has a syntax error; restore it from backup or delete it and let Bloxstrap create a fresh one.

Finding Your Bloxstrap Data Folder

Before you can edit Fast Flags, you need to locate the folder where Bloxstrap stores its configuration files. Open Bloxstrap and look for the Settings button — it's usually a gear icon in the top right or a menu option. Click Settings, then look for a button or link that says "Open data folder" or "Show in Explorer" (on Windows) or "Show in Finder" (on Mac).

This opens a file browser window pointing directly to your Bloxstrap data folder. On Windows, this is typically C:\Users\[YourUsername]\AppData\Local\Bloxstrap. On Mac, it's usually ~/Library/Application Support/Bloxstrap. Inside this folder, you'll see several files and subfolders. Look for ClientSettings.json — this is the file you'll edit to add Fast Flags.

If ClientSettings.json doesn't exist yet, Bloxstrap will create it the first time you launch a game. You can also create it yourself by right-clicking in the folder, selecting "New" and then "Text Document", naming it ClientSettings.json, and saving it.

Opening and Editing ClientSettings.json

Right-click on ClientSettings.json and select "Open with" or "Edit". Choose a plain-text editor — Notepad (Windows), TextEdit (Mac), or any code editor like Visual Studio Code works fine. Do not use Microsoft Word or any word processor, because they add invisible formatting that breaks the file.

When you open the file, you'll see either an empty file or existing code that looks like this:

{   "FastFlags": {     "FFlag::SomeFeatureName": "true"   } }

The structure is always the same: curly braces on the outside, a "FastFlags" section in the middle, and individual flags inside that section. Each flag is a key-value pair separated by a colon, and each pair ends with a comma (except the last one before the closing brace).

Adding Your First Fast Flag

To add a Fast Flag, place your cursor inside the "FastFlags" section and add a new line. Type the flag name in quotes, followed by a colon, then the value in quotes. For example, to enable the frame rate counter, you would add:

"FFlag::DebugDisplayFPS": "true"

If you're adding multiple flags, separate each one with a comma. Here's what a file with three flags looks like:

{   "FastFlags": {     "FFlag::DebugDisplayFPS": "true",     "FFlag::GraphicsQualityPerformance": "3",     "FFlag::DisableMotionBlur": "true"   } }

Notice that the last flag does not have a comma after it. This is critical — JSON format requires commas between items but not after the final item. A missing or extra comma will cause Bloxstrap to reject the entire file.

Common Fast Flags and What They Do

Different Fast Flags control different aspects of Roblox. Some of the most commonly used ones include FFlag::DebugDisplayFPS (shows your frame rate in the top left corner), FFlag::DisableMotionBlur (removes motion blur for clearer visuals), and FFlag::GraphicsQualityPerformance (sets graphics quality from 1 to 21, with lower numbers meaning better performance on older computers).

Other flags reduce memory use, enable experimental rendering modes, or change UI behavior. The exact flag names and values change as Roblox updates its code, so flags that work today may stop working in a future Roblox update, or new flags may become available.

You can find lists of current Fast Flags on community sites and Discord servers dedicated to Bloxstrap and Roblox modding. These communities maintain updated lists because the flags change frequently. Always test a flag in a low-stakes game first — if it causes crashes or severe lag, remove it and restart Bloxstrap.

Saving Your Changes and Restarting

After you finish editing ClientSettings.json, save the file. Use Ctrl+S (Windows) or Cmd+S (Mac), or go to File and click Save. Close the text editor completely. Then close Bloxstrap entirely — don't just close the game window; close the Bloxstrap launcher itself.

Reopen Bloxstrap and launch a game. The Fast Flags take effect only when Bloxstrap starts, not while it's already running. If you changed the frame rate display flag, you should see the FPS counter appear in the top left corner of the game. If you changed graphics settings, you should notice the visual difference immediately.

If Bloxstrap fails to launch after you edited the file, the ClientSettings.json file likely has a syntax error — a missing comma, mismatched quotes, or extra characters. Open the file again and check for typos. If you can't find the error, delete the file entirely, restart Bloxstrap, and let it create a fresh ClientSettings.json. Then add your flags more carefully, one at a time.

Troubleshooting Syntax Errors

The most common problem is a syntax error in the JSON format. JSON is strict about punctuation: every opening brace needs a closing brace, every key and value must be in quotes, and commas must separate items but not appear after the last item. A single missing comma or quote will break the entire file.

If Bloxstrap won't launch, open ClientSettings.json again and look for these mistakes: missing commas between flags, a comma after the last flag, mismatched quotes, or typos in the flag name itself. Some text editors highlight syntax errors in different colors, which makes them easier to spot. If your editor doesn't, try copying your code into an online JSON validator (search "JSON validator" in your browser) — it will point out exactly where the error is.

Another common issue is editing the file while Bloxstrap is running. Always close Bloxstrap completely before you edit ClientSettings.json, and always restart Bloxstrap after saving changes. If you edit the file while Bloxstrap is open, your changes may not take effect, or Bloxstrap may overwrite your edits when it closes.

Frequently Asked Questions

Do Fast Flags work with the official Roblox launcher?

No. Fast Flags only work through Bloxstrap because Bloxstrap reads the ClientSettings.json file and passes those flags to Roblox when it launches. The official Roblox launcher doesn't have this feature. This is one of the main reasons players use Bloxstrap instead of the standard launcher.

Will using Fast Flags get me banned?

Fast Flags are Roblox's own internal settings, not cheats or exploits. Using them to adjust graphics, enable frame rate counters, or test experimental features does not violate Roblox's terms of service. However, some flags may cause visual glitches or crashes. Use flags responsibly and avoid any that claim to give you in-game advantages or bypass security systems.

What happens if I add a flag that doesn't exist?

If you add a flag name that Roblox doesn't recognize, Bloxstrap simply ignores it — it won't cause an error or crash. The flag just has no effect. This is why typos in flag names are hard to catch; the file launches fine, but the flag you wanted doesn't actually do anything.

Can I add flags to a game that's already running?

No. Fast Flags take effect only when Bloxstrap launches. If you edit ClientSettings.json while a game is running, close the game and restart Bloxstrap for the changes to take effect. You cannot hot-reload flags without restarting.

Where do I find new Fast Flags to try?

Community Discord servers and forums dedicated to Bloxstrap maintain lists of current Fast Flags. Search for "Bloxstrap Fast Flags" or "Roblox Fast Flags" online, or join Bloxstrap community servers where players share flags they've tested. Always verify a flag with multiple sources before adding it, because outdated or incorrect flag names won't work.