Roblox FFlag Watcher

Roblox FFlag Watcher

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What is it?

Roblox FFlag Watcher is a web app and server that watches and displays FFlag changes.

What is a Fast Flag (FFlag)?

The Roblox engine uses a system called Fast Flags as part of its deployment process. When code is shipped, not all of it is active by default. Rather, the changes are suppressed by flags that are dynamically enabled and disabled, even after the code is live on production.

Why should I care?

Sometimes, when a part of your game stops working without you changing anything, the reason is actually that a FFlag was changed since you last tested. Since Roblox changes these flags throughout the day, it’s possible that a newly enabled change will break something in your game.

I’ve personally wasted too much time trying to figure out why my code stopped working without me touching it, only to find out hours later that a recently changed FFlag was the root cause of the problem.

Next time you find yourself in a similar scenario when your code inexplicably stops working, checking against the FFlag tracker history can potentially save you time and help you give Roblox more useful information so that the root problem can be addressed more quickly.


Each FFlag has its own comment section next to its history where anybody can provide information, speculate, or link relevant DevForum posts. Here’s an example. I don’t expect people to comment all that often, but the option is there at least.


Thanks for checking out my latest project. I hope you find it useful and that it saves you time! If you have any suggestions or feedback, feel free to let me know with a reply or a GitHub issue.

– evaera


How interesting! Just out of curiousity, how long did this take you to do?

I started working on it on the 17th at 6:41 PM and mostly finished it around 6:44 AM on the 18th. Made a few additions later on yesterday and today throughout the day. Commit history


This is really cool! However it is a bit hard to read the pages on mobile (I’m on Android, specifically Samsung Galaxy S8). I had to switch to desktop mode to read this.

Other than that it looks great and this will be very useful in the future. Thanks!

1 Like

Yeah – didn’t optimize it for mobile yet. I may do a pass in the future to fix the chips and Value field so that they adjust correctly on smaller screens.


This may seem off-topic, but your CSS on your apps are always amazing to look at. I’m surprised you made this in such a short amount of time, really skillful and amazing!


This site was previously suffering from some performance issues (taking ages to load) after collecting about a year’s worth of changes. I just made some changes to fix these issues so now it should load quickly and be usable again for everyone.


Just gotta say, it’s really good!

Very simple to use and useful tool. Thank you so much evaera!

Optimized for mobile now!


Ongoing thanks for continuing to support this tool. I love it!