Assetto Corsa Competizione needs no telemetry setting. It publishes its data in shared memory on its own, so you start Horizon Labs, select the game, add one browser source in OBS and drive. This page covers the steps, what ACC sends, and what to check when nothing moves.
Steps
- Start Horizon Labs and open the Connection section of the settings. Under Game, choose Assetto Corsa Competizione. The hint under the selector reads “nothing to enable in game”, and the IP and port fields are greyed out because shared memory has none.
- Set the display mode. In the Overlay settings, set Display mode to OBS (browser source), or to Both if you also want the HUD on screen while you drive.
- Add a browser source in OBS with the URL
http://127.0.0.1:8088/overlay/index.html. If you changed the OBS port in Horizon Labs, use that port instead. The URL is also shown in the Overlay settings. - Match the canvas. Give the source the size of your OBS canvas, for example 1920×1080, and place it above your game capture. Horizon Labs has a canvas option (1080p, 1440p, 4K, ultrawide, 32:9, or auto from the source size) so the layout fits.
- Start a session in ACC. The HUD goes live once you are on track.
For the general OBS workflow, including Streamlabs, Meld Studio and TikTok LIVE Studio, see Add a live telemetry HUD to OBS.
Borderless mode: when it matters
There are two ways to show the HUD, and only one cares about the game window.
- On-screen overlay (Overlay or Both mode): run ACC in a windowed or borderless window. Exclusive fullscreen can hide or clip a window drawn above the game.
- OBS browser source: the HUD is rendered by OBS, not drawn on top of ACC, so the game’s window mode does not change it. Your game capture still has to see the game, so use Game Capture or Window Capture as you normally would.
If you only need the HUD on stream and want ACC in exclusive fullscreen, set the display mode to OBS and leave the on-screen overlay off.
What ACC gives the HUD
Horizon Labs reads ACC’s shared memory and fills these fields:
- Engine
- Speed (km/h and mph), RPM, rev limit, gear, boost
- Inputs
- Throttle, brake, clutch, steering
- Race
- Lap number, current lap, last lap, best lap, position, fuel
- Dynamics
- Longitudinal, lateral and vertical g-force, pitch, roll, heading, drift angle, tyre temperatures for all four tyres
- Car
- Car name
ACC does not publish suspension travel, so suspension widgets stay idle there. The full per-game list is on the Assetto Corsa and ACC page.
GT3-style templates
ACC is a GT3 game, and the Designer’s HUD store includes a GT3 Display template for it: a wheel-display layout with a carbon bezel, an LED shift row, a lit gear window, pedal traces, a g-force puck and the four tyre temperatures. It uses only fields ACC sends. Open it in the Designer, change colours, fonts or layout, then send it to the overlay in one click. The walkthrough is in Build your first HUD.
Anything you build also shows on stream, because the OBS page renders the same HUD as the in-game overlay.
Choosing what to show on stream
A stream HUD works best when viewers can read it in a second. From the ACC fields above, these tend to carry a broadcast:
- Gear, speed and RPM with a shift indicator, which tell viewers how hard you are pushing.
- Throttle and brake traces, which show braking points and trail braking at a glance.
- Current, last and best lap, so a viewer can follow your pace without a timing screen.
- Tyre temperatures, useful in a long GT3 stint where the tyres change how the car feels.
Keep the HUD small in a corner so it does not cover the racing line. If you stream on an ultrawide or 32:9 canvas, pick the matching canvas option in Horizon Labs so the layout does not stretch.
Check that data is arriving
The Connection section has a Live status block that shows the last packet time and packet count, and Diagnostics lists the telemetry state. If those do not move while you drive, the problem is between ACC and Horizon Labs. If they move but OBS is blank, the problem is the browser source.
Troubleshooting
The HUD stays empty or shows zeros
- Check the game selector. It must say Assetto Corsa Competizione, not Assetto Corsa. The two are separate profiles.
- Be on track. Horizon Labs only draws new frames while a session is live. In menus, or with the sim paused, the HUD holds its last frame.
- Check the browser source. Open the same URL in a normal browser. If it loads there but not in OBS, refresh the source or restart OBS. If it loads nowhere, check that Horizon Labs is running and that the OBS port matches the URL.
Does it matter whether Horizon Labs or the game starts first?
No. ACC creates its shared memory only while it runs, and Horizon Labs treats a missing game as “waiting” and retries about once a second. Start either one first. If you closed ACC, the HUD can stay on its last frame until you start a new session.
The overlay is fine in OBS but missing on screen
That is the window mode: switch ACC to windowed or borderless, or set the display mode to OBS only.
Good to know
- Horizon Labs only reads the telemetry the game publishes. It does not inject into ACC or edit its files. Each game’s own terms still apply.
- Streaming from a second PC? Turn on LAN mode and read HUD on a second PC. Note that ACC’s shared memory is local to the PC running the game, so Horizon Labs must run on that PC.