If you've spent any time in Studio lately, you've probably realized that a solid roblox run service script is basically the backbone of any smooth-running game loop. It's one of those things that separates a jittery, laggy mess from a professional-feeling experience. Whether you're trying to move a part smoothly, update a custom camera, or keep a UI element pinned to the mouse, you're going to be reaching for RunService pretty quickly.
The thing about Roblox is that the standard task.wait() or the old-school wait() just doesn't cut it for high-performance tasks. They're fine for a simple cooldown or a delay, but if you want something to happen every single frame, you need a different approach. That's where RunService comes in, and honestly, once you get the hang of it, you'll wonder how you ever built anything without it.
Why We Stop Using Wait()
We've all been there—trying to make a door slide open or a platform move by using a while true do loop with a task.wait() inside. It works, sure, but it looks choppy. The reason is that wait() isn't synced to the game's actual frame rate. It's basically telling the engine, "Hey, wake me up whenever you feel like it after this much time."
When you use a roblox run service script, you're hooking your code directly into the game's internal heartbeat. Instead of guessing when the next frame is going to happen, the script waits for the engine to say, "Okay, I'm about to render the next frame, do your thing now." This synchronization is what makes movements look buttery smooth. If you're building something competitive or visually polished, you really can't afford to skip this.
The Big Three: Heartbeat, RenderStepped, and Stepped
RunService isn't just one big button; it's divided into a few different events, and choosing the wrong one can actually make your game perform worse. Most of the time, you'll be looking at Heartbeat, RenderStepped, and Stepped.
Heartbeat: The General Purpose Workhorse
Heartbeat is probably what you'll use 90% of the time in a roblox run service script. It fires every frame after the physics simulation has finished. If you're moving a non-physics object, updating a timer, or checking distances between players, this is your best friend. It runs on both the server and the client, though you should be careful about running too much heavy logic on the server-side Heartbeat because that's a quick way to kill your server's performance.
RenderStepped: Only for the Client
This one is special. It fires before the frame is rendered on the screen. Because of that, it only exists on the client (the player's computer). You should only use RenderStepped for things that are purely visual, like a custom camera script or a weapon model that follows the player's view. A word of caution, though: if your code in RenderStepped takes too long to run, the player's FPS will literally drop. The engine has to wait for your script to finish before it can show the player the next frame. Use it sparingly.
Stepped: The Physics Friend
Stepped fires before the physics simulation. If you're doing something complex with manual velocity calculations or you need to adjust a part's position right before the engine calculates how it hits something else, Stepped is the way to go. It's less common for general gameplay scripts but essential for custom physics engines or character controllers.
Setting Up a Basic Script
Actually writing a roblox run service script is pretty straightforward. You just need to get the service and then connect a function to one of the events. It usually looks something like this:
```lua local RunService = game:GetService("RunService")
RunService.Heartbeat:Connect(function(deltaTime) -- Your magic happens here end) ```
The deltaTime (often shortened to dt) is the most important part of that function. It tells you exactly how much time has passed since the last frame. This is crucial because not everyone plays at 60 FPS. Some people might be on a beefy PC hitting 240 FPS, while others are on an old phone struggling to reach 30. If you move a part by 1 stud every frame, the person with 240 FPS will see that part zoom away way faster than the person on the phone. By multiplying your movement by deltaTime, you ensure the part moves at the same speed regardless of the frame rate.
Keeping Things Optimized
It's easy to get carried away and start putting every single bit of logic into a roblox run service script. I've seen scripts where people are doing massive table searches or complex Raycasts sixty times a second. Don't do that.
The goal is to keep your RunService functions as "lean" as possible. If you don't need to check something every single frame, maybe check it every 0.1 seconds instead using a simple timer. You can even use the deltaTime to create a custom throttle. For example, if you want a piece of code to run roughly 10 times a second instead of 60, you can accumulate dt into a variable and only run your logic when that variable hits 0.1.
Another thing to remember is disconnecting your connections. If you have a script that connects to Heartbeat when a player opens a menu, but you never disconnect it when they close the menu, that script is going to keep running in the background forever. That's a classic memory leak. Always store your connection in a variable and call :Disconnect() when it's no longer needed.
When to Use Server vs. Client
Choosing where to put your roblox run service script is a big deal for game feel. If you're moving a platform on the server, players might notice a tiny bit of jitter because of network latency. For things that need to be "perfect" to the eye, like a player's own movement or UI animations, you almost always want to do that on the client.
However, if it's a platform that multiple players are standing on, you usually need the server to handle the "real" position so everyone stays synced up. It's a bit of a balancing act. Usually, you'll have the server handle the logic and the client handle the "smoothing" or visual representation.
Real-World Example: A Smooth Floating Part
Let's say you want a gem to hover up and down. You could use a Tween, but maybe you want more control, or you want it to react to things in real-time. A roblox run service script using a sine wave is perfect for this.
```lua local RunService = game:GetService("RunService") local gem = script.Parent local counter = 0
RunService.Heartbeat:Connect(function(dt) counter = counter + dt local yOffset = math.sin(counter * 2) * 0.5 gem.CFrame = gem.CFrame * CFrame.new(0, yOffset, 0) end) ```
In this case, the counter keeps track of time, and the math.sin function gives us that nice, smooth oscillating motion. Because we're using dt, the floating speed stays consistent even if the server starts to chug a bit.
Final Thoughts
Mastering the roblox run service script is really about understanding the game's rhythm. Once you stop thinking in terms of "wait a second" and start thinking in terms of "what needs to happen this frame," your scripting skills take a massive leap forward.
Just remember: keep it light, use deltaTime for everything, and always pick the right event for the job. Heartbeat for general stuff, RenderStepped for the camera/visuals, and Stepped for physics. If you stick to those rules, your games are going to feel a whole lot more responsive and professional. It takes a little bit of practice to get the math right, but once you do, you'll never want to go back to basic loops again. Keep experimenting with it, and you'll see exactly what I mean.