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Playing with friends? Godlike.Host runs hosted Assetto Corsa servers from 10 data-center locations, with free DDoS protection.
To add online AI traffic, run an AI-capable server such as AssettoServer, enable AI in cfg/extra_cfg.yml, place a spline that belongs to the selected track layout in that track’s ai/ folder, and declare traffic cars in entry_list.ini. Clients must have matching cars and track files, plus compatible Content Shaders Patch (CSP) and Content Manager versions.
After the server starts, verify locally through Drive > Online > LAN, join with the configured player car, and drive out of the pits. AI cars begin spawning at that point. Internet players additionally need a reachable server, correct port forwarding or public-list configuration, and an invite method that is usable outside your local network.
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Assetto Corsa’s ordinary single-player AI does not automatically become multiplayer traffic. The server must create and synchronize the AI cars. AssettoServer is a custom Assetto Corsa server designed for freeroam play and can load one or more AI splines to provide traffic. The spline is the racing line that tells each AI car where it may drive; the server-side configuration decides whether AI is enabled and which car entries are spawned.
This distinction explains why traffic can work offline but disappear online. An offline session can read the spline from your local installation, while an online session depends on the dedicated server having the spline, enabled AI, traffic entries, and compatible content. Installing a traffic mod only on the client does not satisfy those server requirements.
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- Extremely detailed with single player and multiplayer options, exclusive licensed cars reproduced with the best accuracy possible, thanks to the official cooperation of Car Manufacturers.
- ASSETTO CORSA has been developed at the KUNOS Simulazioni R&D office, located just inside the international racing circuit of Vallelunga, allowing the team to develop the game with the cooperation of real world racing drivers and racing teams.
Prerequisites and compatibility
Prepare the following before editing configuration files:
| Requirement | What to verify | Why it matters |
|---|---|---|
| AssettoServer files | The host machine has a complete AssettoServer installation, kept separate from the game installation when following the current installation guidance. | The dedicated server needs its own configuration, content tree, and executable files. |
| Track layout with an AI spline | The exact layout selected by the server includes a compatible fast_lane.ai or fast_lane.aip. |
AI cannot navigate a layout that has no usable spline. A spline from another map or layout is not a safe substitute. |
| Matching content | Server and every client have the same track layout and car content, including compatible versions. | Missing or different files commonly prevent joining or produce checksum errors. |
| Client software | For the documented Steam-authenticated flow, use CSP 0.1.75 or newer and Content Manager v0.8.2297.38573 or newer. | Older client components may fail authentication or fail to interpret server options correctly. |
| Text-editor access | You can edit YAML, INI, and server configuration files without changing their extensions. | The traffic switch and car declarations are plain-text settings. |
| Network access | For friends outside your LAN, the host can receive forwarded game-server traffic and advertise or share a public connection method. | A local address works only for devices that can reach the same private network. |
Set up AssettoServer traffic step by step
1. Install the dedicated server separately
Install or extract AssettoServer according to its current documentation. Keep the server directory separate from the main Assetto Corsa game directory. This separation makes it clear which files are authoritative for online players and prevents an update to the game installation from silently replacing server configuration.
Start with a known-good server configuration and the same track and car packages that you intend to give players. Do not troubleshoot AI with several untested maps or large content packs at once; first make one layout work.
2. Enable AI in extra_cfg.yml
Open the server’s cfg/extra_cfg.yml. Add or edit the AI switch so it reads exactly:
EnableAi: trueYAML indentation and spelling matter. Keep the key at the level used by the existing file, use a lower-case true, and avoid adding quotation marks or tabs. Save the file in the server’s cfg directory, not in your client’s game folder.
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- Assetto Corsa features an advanced DirectX 11 graphics engine that recreates an immersive environment, dynamic lighthing and realistic materials and surfaces.
- Extremely detailed with single player and multiplayer options, exclusive licensed cars reproduced with the best accuracy possible, thanks to the official cooperation of Car Manufacturers.
- ASSETTO CORSA has been developed at the KUNOS Simulazioni R&D office, located just inside the international racing circuit of Vallelunga, allowing the team to develop the game with the cooperation of real world racing drivers and racing teams.
3. Install the spline in the matching track folder
In the server content tree, open:
content/tracks/<trackname>Create an ai directory if one is not already present. Copy the spline supplied for that exact track layout into it. The common filenames are:
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content/tracks/<trackname>/ai/fast_lane.aicontent/tracks/<trackname>/ai/fast_lane.aip
Use the filename and format provided by the track author. Do not rename a spline merely to make it look familiar, and do not copy a Shutoko Revival Project spline into another map. The current AssettoServer introduction says its default AI settings are tuned for Shutoko Revival Project; another map may require different values and a spline built for its own roads.
Layouts are separate content. If a track has several layouts, select the layout whose folder contains the spline and ensure the server’s configured layout points to that same folder. A valid spline in an unused layout will not produce traffic.
4. Add traffic cars to entry_list.ini
Open the server’s entry_list.ini. Keep your player-car entry, then add one entry for each AI vehicle you want available as traffic. The beginner configuration uses AI=fixed for traffic cars. Preserve the existing model, skin, and setup fields from cars that are known to load on your server.
[CAR_0]
MODEL=your_player_car
SKIN=0
[CAR_1]
MODEL=your_traffic_car
SKIN=0
AI=fixed
[CAR_2]
MODEL=another_traffic_car
SKIN=0
AI=fixedThe model and skin values above are illustrative field names; use the actual car folders and skins installed on both server and clients. The important traffic declaration is AI=fixed. If you add cars but omit the AI parameter, the server has no instruction to use those entries as fixed AI traffic. If you set every entry as AI, you may leave yourself no selectable player car, so retain at least one normal player entry.
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- Even the secondary details are faithfully reproduced to make you feel the thrill of being in the cockpit of a real racing car. Doors, windshield wipers, headlights, racing lights, racing equipment and control devices such as ABS, traction control, engine ignition and ECU mapping, are all under the driver’s management to assure the best performance and offer the player total control of the car.
- Thanks to Laserscan technology, every official circuit is recreated with the utmost accuracy: all curbs and details perfectly fit their real counterparts to grant a gaming experience as faithful to reality as possible.
- A well-structured ranking system will evaluate individual performance and driving behaviour to reward the most virtuous drivers and promote fair play in online competitions. The matchmaking function makes sure that you can compete with opponents of similar skill level and easily find online races to join, while the leaderboards will allow you to compare single-lap performance with virtual pilots from around the world with the same car, circuit and weather conditions.
5. Start the server and perform a LAN test
Start AssettoServer after saving the YAML, track, and entry-list changes. For a local check in Content Manager:
- Open Drive > Online > LAN.
- Select the server you started and choose the configured player car.
- Click Join.
- Drive out of the pits instead of waiting in the garage.
The documented workflow says AI traffic starts spawning after you leave the pits. Give the session a moment to load before treating a short delay as a failure. Watch the server console for file or content errors while you drive.
6. Make the server reachable from the internet
A LAN test proves the configuration, not internet reachability. For friends outside your home network, forward the server’s required ports on the router to the host machine, allow the executable through the operating system firewall, and configure the server’s public-list or invite method. Use the externally generated invite or public address. An invite containing a private address such as a home LAN IP is useful only to devices that can route to that LAN.
Test from a different network, such as a phone hotspot, rather than asking an outside player to retry the same private invite. If the host is behind carrier-grade NAT or another upstream router, ordinary port forwarding may not be enough; the network must provide a reachable public endpoint or you must use a managed service that supplies one.
Client CSP and Content Manager requirements
For Steam-authenticated joining in the documented AssettoServer introduction, clients need CSP 0.1.75 or higher and Content Manager v0.8.2297.38573 or higher. Treat those as minimums for that flow, not as a promise that every third-party track or extension works identically on every later build. Have all players use the same track layout, car versions, and required extensions.
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Content Manager is the practical launch interface for the LAN workflow and for many custom-server settings, but AI itself is supplied by the server. A player cannot fix a server with a local AI toggle. If one friend can join and another cannot, compare the failing client’s CSP, Content Manager, car files, track layout, and checksum state before changing server settings.
Using CSP server options safely
AssettoServer documents a csp_extra_options.ini file for CSP server options, including a way to require a minimum CSP version. Use that file when you need the server to enforce a client capability rather than relying on every player to remember the requirement.
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Make a backup of the original surface file before any CSP edit. If checksums fail after an experiment, restore the backup, confirm that only the first surface entry is changed as documented, and retest with a clean client cache.
Troubleshooting traffic and joining problems
| Symptom | Likely cause | Action |
|---|---|---|
| No AI traffic appears after leaving the pits | AI is disabled, the spline is missing, or the selected layout does not match the spline. | Check EnableAi: true in cfg/extra_cfg.yml; verify the ai folder under the exact track layout; confirm that the file is named and formatted as supplied. |
| The server loads but traffic cars never spawn | There are no traffic entries or they lack the AI declaration. | Open entry_list.ini, retain a player entry, add traffic entries, and set AI=fixed on each intended AI car. |
| Traffic appears on one map but not another | The second map has different spline geometry or needs map-specific AI settings. | Use a spline built for that map and adjust its AI settings instead of copying defaults tuned for Shutoko Revival Project. |
| Friends cannot see or join the server | The host is not reachable, ports are not forwarded, the server is not listed publicly, or the invite contains a private address. | Test locally first, then verify firewall and router forwarding, public-list settings, and the externally generated invite from a separate network. |
| One player is rejected while others join | That client has different track or car files, an incompatible CSP or Content Manager version, or a checksum difference. | Match content and minimum versions, remove unauthorized edits, and compare the client’s exact layout and extension files with the server. |
| Checksum mismatch follows a CSP surface change | More than the permitted first surface entry was edited. | Restore the original file and change only SURFACE_0 to CSPFACE_0 when the documented CSP track-folder method calls for it. |
| AI behaves badly on a custom map | Server defaults are optimized for a different road network, or the spline does not match the map’s lanes. | Use the map author’s compatible spline and tune map-specific AI settings; do not assume a spline from another layout is interchangeable. |
Self-hosting versus managed hosting
Self-hosting gives you direct access to extra_cfg.yml, entry_list.ini, track folders, and CSP options. That control is valuable when you need to install custom splines, test unusual layouts, or change traffic density and car lists frequently. The trade-off is that you must maintain the server files, keep content synchronized, configure firewall and port forwarding, and diagnose network failures.
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A managed server can remove router and maintenance work, but compatibility is not automatic. Before paying for one, ask the provider to confirm that it runs AssettoServer rather than only a standard Assetto Corsa server, permits custom AI spline files in the track’s ai directory, allows the required entry_list.ini settings, supports CSP server options, and provides enough network capacity for your intended player count.
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|---|---|---|
| Configuration control | Full access to YAML, INI, track, and CSP files. | Depends on the provider’s panel and file-access policy. |
| AI spline installation | Copy files directly into the server track folder. | Must be explicitly supported; some hosts restrict custom content. |
| Networking | You handle public reachability, firewall rules, and port forwarding. | Provider normally supplies an internet-reachable endpoint. |
| Maintenance | You apply updates, backups, and troubleshooting. | Some maintenance is outsourced, but update timing and support quality vary. |
| Performance and player count | Limited by your CPU, memory, upload bandwidth, and home network. | Depends on the plan’s hardware, bandwidth, and provider limits; obtain the supported AI traffic and player count in writing. |
| Best fit | Technical users who want maximum control and already have a reachable host. | Groups that value simpler networking and predictable availability over file-level control. |
Keeping a traffic server reliable
Back up before changing content
Keep copies of extra_cfg.yml, entry_list.ini, csp_extra_options.ini, and the working track ai folder. A small configuration backup lets you undo a failed spline or CSP experiment without rebuilding the server.
Change one variable at a time
When diagnosing a failure, first verify AI with one known-good layout and a small number of traffic cars. Then add additional cars, CSP options, or a new map separately. This isolates whether a problem comes from the spline, the entry list, client content, or networking.
Keep map and spline versions paired
Treat the AI spline and map layout as one release. Updating a track while retaining an older spline can place AI on invalid coordinates or lanes. Distribute the same track version and layout name to the server and every player.
Plan for client updates
When CSP or Content Manager changes, retest Steam-authenticated joining and any enforced minimum version before announcing the server to friends. A server that works for the host can still reject clients with older software or modified content.
Quick Recap
Essential configuration checklist
- AssettoServer is installed in its own server directory.
EnableAi: trueis present incfg/extra_cfg.yml.- The selected track layout has its matching
fast_lane.aiorfast_lane.aipundercontent/tracks/<trackname>/ai. entry_list.inicontains a selectable player car and traffic entries usingAI=fixed.- Server and clients have identical track, layout, car, and skin content where required.
- Clients meet CSP 0.1.75+ and Content Manager v0.8.2297.38573+ for the documented Steam-authenticated flow.
- The LAN test works when a player joins and drives out of the pits.
- Internet players receive a public invite or address, not a private LAN IP.
- Any CSP surface edit changes only the first surface entry as documented.
- Map-specific AI settings are reviewed when moving beyond Shutoko Revival Project.
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