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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →To make an NPC behave consistently for everyone in a Roblox multiplayer server, run its target selection and pathfinding in a server-side Script. Use PathfindingService to compute a route, move the NPC’s Humanoid through its waypoints, and recompute when the route is blocked or out of date. Keep attacks, damage, rewards, and other shared decisions on the server too.
What makes an NPC “AI” in this setup?
Here, AI means scripted behavior: the NPC selects a player, calculates a route, and responds to changes such as an obstacle or a target moving away. This approach uses Roblox Studio’s built-in services; it does not require a separate AI product.
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A moving character model needs a Humanoid and a usable root part, commonly named HumanoidRootPart. The server script chooses a target and issues movement commands. Roblox’s pathfinding guide describes computing paths and moving Humanoids through waypoints.
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Why should shared NPC behavior run on the server?
Roblox uses a client-server model: the server is authoritative for shared game state, while clients display the replicated world and handle local presentation. If each player’s client independently controls an NPC, players can see different decisions or movement. A server-controlled NPC gives the experience one decision-maker.
Server pathfinding also avoids a streaming issue: a client may not have distant or streamed-out objects in its local world and therefore may not be able to calculate a route involving them. For an NPC that should navigate consistently for everyone, compute its route on the server.
Roblox Creator Hub’s security guidance puts the principle plainly: “The server must be the ultimate source of truth for all simulation states, rules, player progression, and critical decisions.” See Security and cheat mitigation tactics.
Set up the NPC and server script
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Insert or build a rig with a
HumanoidandHumanoidRootPart, then place it inWorkspace. Make sure the parts are configured so the Humanoid can move; anchoring the rig in a way that prevents movement will stop it.Do these 3 things before closing this tab:
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Put the controlling code in a server
Script. UseServerScriptServicefor shared game logic, or put a serverScriptin the NPC model if its behavior belongs with that model. If you use an unusual location, check Studio’s current Script type andRunContextguidance. -
On the server, choose an eligible target. Check that the player’s character exists, that it is alive if your game requires that, and that it has a usable root position. Set explicit rules for target range and when the NPC should switch targets.
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Create a path using
PathfindingService:CreatePath(). Set agent parameters to approximate the NPC’s dimensions and movement abilities, then compute a route from the NPC’s root position to the target’s position. -
Check that the path status indicates success before reading its waypoints. Move the Humanoid along the route, honoring waypoint actions such as jumps when needed.
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Roblox’s pathfinding documentation covers path computation, waypoint movement, and blocked-path handling. A path can fail if the destination is unreachable, the agent dimensions do not suit the rig, or the start or destination is not on navigable geometry. Treat failure as a normal condition; do not assume a waypoint list exists.
Keep paths current without recalculating constantly
A calculated route can become unusable if something blocks it or the target moves far enough to make the route stale. Listen for Path.Blocked and recompute when the blocked waypoint is still ahead on the NPC’s route. A blockage behind the NPC does not necessarily require a new path.
Use bounded waits and handle computation or movement failures so the NPC does not stall indefinitely. Recalculate when the target’s movement makes the current route meaningfully outdated, but do not recompute every frame. There is no single official update interval that suits every map, NPC count, and server workload; tune the cadence to the experience and observe server performance.
Server pathfinding or client pathfinding?
| Choice | What it means | Best fit |
|---|---|---|
| Server-computed path | The server selects the target and computes the route using its view of the world; NPC decisions are shared. | Shared NPCs whose behavior should be consistent for every player, especially in experiences using streaming. |
| Client-computed path | A client computes a route using the world objects available to that client; streamed-out objects may be missing. | Local, cosmetic behavior that does not determine shared game outcomes. |
For a multiplayer NPC that pursues players or affects gameplay, server computation is the practical default. Roblox’s pathfinding guide discusses the streaming limitation, and its security guidance explains why consequential decisions should not be trusted to clients.
Keep interactions and consequences authoritative
If a client needs to request an interaction, a RemoteEvent can carry that request. It does not make the request valid: clients can submit fabricated arguments or fire events at excessive rates. Before changing NPC or game state, validate the player’s state, distance, permitted action, cooldown, and argument shape on the server. Do not accept a client-supplied target or reward as authoritative without checking it.
Best Value
Keep target selection, hit decisions, damage, loot, progression, and other shared outcomes on the server. Clients can render the replicated NPC and handle cosmetic presentation. Roblox explains event direction and the client-server boundary in Remote events and callbacks.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Should you force server physics ownership?
Server-side AI and server-owned physics are related, but they are separate choices. The server can make the NPC’s decisions while Roblox automatically assigns an unanchored physics assembly to a nearby client for simulation. For eligible assemblies, a server script can call SetNetworkOwner(nil) to force server ownership. Roblox warns that forcing ownership can make motion feel jittery, so use it only when the control or security need outweighs that trade-off. Anchored parts remain server-owned, and ownership calls cannot change that.
| Ownership choice | Trade-off | Use when |
|---|---|---|
| Automatic ownership | Roblox can distribute physics simulation to nearby clients. | The NPC’s physics does not require stricter server control and its movement behaves acceptably. |
| Forced server ownership | Gives the server physics control for an eligible unanchored assembly, but can make visible motion jittery. | The NPC’s physical state needs tighter control and the resulting motion remains acceptable. |
See Roblox Creator Hub’s network ownership guide for automatic ownership, server ownership, and the trade-offs.
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Test the behavior in a multiplayer session
Use Studio’s server-and-client testing rather than relying only on a solo run. Add obstacles and test blocked routes, a target that moves, and a target that dies or respawns. If the experience uses streaming, test with streaming enabled. Studio’s network simulation tools can add latency.
- NPC does not move: Check that the model has a live
Humanoidand root part, that its parts are not anchored in a movement-blocking configuration, and that the controlling script is running on the server. - Path status is not successful: Check whether the destination is reachable, the agent parameters fit the rig, and the start and destination are on navigable geometry. Handle the failure before accessing waypoints.
- NPC gets stuck after starting: Check whether the route is blocked ahead and whether the script recomputes when that blockage affects the remaining path.
- It works alone but not on a server: Check script execution context, replication, network ownership, and assumptions about what the server or client can see. Reproduce the problem in a multi-client Studio session.
- One client finds a path and another does not: Streaming may leave one client without relevant world objects. Calculate shared NPC routes on the server.
- Players can exploit an interaction: Validate the action, distance, player state, arguments, and rate on the server before applying consequences.
When the broader server authority model is relevant
Putting NPC logic in a server script does not require enabling Roblox’s broader server authority model. That model is a wider networking architecture with setup requirements and concepts such as prediction and rollback. Consider it separately if the game’s architecture calls for it, and check Roblox’s current server authority model documentation for its status and requirements.
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