SimHub overlays: dashboards on top of the game
Last updated · SimHub 9.11.22
A SimHub overlay is an ordinary Dash Studio dashboard rendered as a borderless, transparent window sitting on top of the game. It is not injected or hooked rendering, which is why the game must run in windowed or borderless windowed mode — a true fullscreen game owns the display and nothing can sit above it. Overlays have a hard size limit of 480,000 pixels: 800×600 works, 800×800 does not. And despite what several guides claim, VR is not natively supported.
Overlays are the answer for single-monitor setups, which is most people. They are also the SimHub feature with the most misinformation attached to it, so two corrections are near the top.
How overlays actually work
This is worth understanding because it explains every limitation that follows.
SimHub does not inject anything into the game, and it does not hook the game's rendering the way an FPS counter or a screenshot tool does. An overlay is a normal Windows window: borderless, always on top, with a transparent background, drawing a dashboard.
That design choice has real advantages — nothing is modified in the game process, so there is no anti-cheat exposure and no risk of destabilising the game. It also produces the constraints below, all of which follow from the same fact.
The consequence, in one sentence.If a window cannot be placed above your game, an overlay cannot be either — because that is all an overlay is.
The game must not be in exclusive fullscreen
A game in true exclusive fullscreen takes ownership of the display output. Nothing else can draw on top of it, including SimHub.
- Set the game to windowed or borderless windowed. Borderless is what almost everyone wants — it looks identical to fullscreen and permits overlays.
- Vsync is strongly suggested in this mode. Without it, tearing between the composited layers is noticeable in a way it is not in exclusive fullscreen.
- A few games need launch parameters to run borderless properly. Automobilista 2 and Project CARS 2 both want Steam launch options for this.
Modern borderless windowed mode costs very little compared to exclusive fullscreen on current Windows versions, so this is rarely the compromise it once was.
The 480,000-pixel limit
Width × height must not exceed 480,000 pixels.800×600 is exactly 480,000 and is accepted. 800×800 is 640,000 and is rejected. This is a hard limit, not a recommendation, and hitting it is the reason an overlay you designed will not run.
| Size | Pixels | Allowed? |
|---|---|---|
| 800 × 600 | 480,000 | Yes — exactly at the limit |
| 1000 × 480 | 480,000 | Yes |
| 1200 × 400 | 480,000 | Yes |
| 800 × 800 | 640,000 | No |
| 1920 × 300 | 576,000 | No |
| 1600 × 300 | 480,000 | Yes |
The important subtlety: transparent area counts. An overlay surface is composited whether or not anything is drawn on it, so a mostly-empty 1920-wide overlay costs the same as a full one. Size the overlay to fit its content, and use several small overlays rather than one large mostly-empty one.
VR is not natively supported
This is a correction, and it contradicts several guides you will find.An official statement on the SimHub forum: "No VR is not natively supported, but I know it's possible to integrate overlays with software like OVRdrop." Any page claiming SimHub renders overlays into VR natively is wrong.
The reason follows from the mechanism. An overlay is a desktop window, and a VR headset is not showing your desktop — it is showing what the game renders into the headset. A window placed above a desktop application is not in that image at all.
What does work:
- Third-party VR desktop software. OVRdrop and similar tools place desktop windows into the VR view. This is the documented route, and it is a separate product doing a separate job.
- Motion and haptics work perfectly in VR. They do not need rendering — they drive hardware. Bass shakers, LEDs, wind and motion are entirely unaffected by the headset.
- A physical dash still works. Which is admittedly of limited use when you cannot see it.
So the honest position for a VR driver: use SimHub for haptics and hardware output, where it is excellent, and use either an in-game overlay or a VR desktop tool for information.
Turning overlays on and off
A recurring community request with an open issue attached to it: there is no straightforward built-in way to toggle overlays on and off mid-session.
Being the page that says that plainly is more useful than implying a setting exists. The workarounds people use:
- Build the toggle into the dashboard itself — an element bound to a property, driven by a button through Control Mapper or the Keyboard Emulator plugin, that hides content conditionally.
- Use multiple screens within one dashboard, with a near-empty screen as the "off" state, and bind NextScreen to a wheel button.
- Close and reopen the overlay, which is crude but reliable.
The second is the neatest, because screen switching is a first-class feature with six bindable actions already provided.
Making an overlay that is actually usable
- Put it where you are already looking. An overlay in a corner you never glance at is decoration. Just below the apex of your normal sightline is the useful place.
- Fewer elements than a dashboard. An overlay competes with the road. Three or four values is the realistic budget.
- Mind the size limit while designing, not after. Discovering the limit when you try to run it means redesigning.
- Use partial transparency carefully. A fully opaque panel blocks the track; a very faint one is unreadable against a bright sky. Test at both ends of a day/night cycle if the game has one.
- Vsync on. Tearing across a composited overlay is more visible than tearing in the game.
Common questions
Does SimHub work in VR?
Overlays do not — VR is not natively supported, per an official statement on the SimHub forum, which notes that integration is possible through third-party software such as OVRdrop. Motion, haptics, LEDs and wind all work perfectly in VR, because they drive hardware rather than needing to be rendered into the headset.
Why won't my SimHub overlay show up?
Almost always because the game is in exclusive fullscreen. An overlay is a normal borderless window placed on top, and nothing can be placed on top of an exclusive-fullscreen game. Switch the game to windowed or borderless windowed.
What is the maximum SimHub overlay size?
Width multiplied by height must not exceed 480,000 pixels. 800×600 is exactly at the limit and works; 800×800 is 640,000 and is rejected. Transparent area counts towards it, so a mostly-empty large overlay is no cheaper than a full one.
Do SimHub overlays trigger anti-cheat?
SimHub does not inject into the game or hook its rendering — an overlay is an ordinary transparent window drawn above it. That is a deliberately conservative design. Anti-cheat policies are ultimately the game's to state, but nothing is modified in the game process.
How do I turn a SimHub overlay off during a session?
There is no straightforward built-in toggle, and it is a known open request. The neatest workaround is to build several screens into the dashboard with a near-empty one as the off state, and bind NextScreen to a wheel button.
Do overlays cost performance?
Yes — the surface is composited every frame whether or not anything is drawn on it, so transparent area is not free. Keep overlays small and use several rather than one large mostly-empty one. See the performance page for the wider picture.
Sources
Related guides
SimHub is developed independently by Wotever and is not affiliated with oesimracing. This page was checked against SimHub 9.11.22 on 4 August 2026; where the interface has moved on since, the version stamp tells you how far. More on what SimHub is and what it costs.