Half the FFB and haptics advice on this site — including mine — eventually says the same sentence: "open Documents\iRacing\app.ini." I counted eight pages here that send you there.

Not one of them tells you what the file actually is, what happens if you get it wrong, or why the settings you carefully typed in sometimes vanish. That's a dead end I put in front of readers, so here's the page that closes it.

What app.ini actually is

It's a plain text file. Not a database, not encrypted, not signed. Windows will open it in Notepad if you double-click it, and iRacing's own support documentation tells you to do exactly that.

It holds sim-side settings that live outside the in-game menus — things iRacing either never built a slider for, or built a slider for later and left the text entry in place. Networking behaviour, spotter timing, force feedback plumbing, per-effect haptic gains, pit-stop automation defaults.

The important mental model: the menus and the file are two doors into the same room. Change something in Options and iRacing writes it into the file. Change it in the file and the sim reads it at launch. That's also the reason for the single most common way people lose their edits — more on that below.

Where the file lives

iRacing's support documentation gives the folder path verbatim:

the full file path of this folder is C:\Users< your user >\Documents\iRacing

So the file itself is C:\Users\<your user>\Documents\iRacing\app.ini.

That folder is not your iRacing install. The install defaults to C:\Program Files (x86)\iRacing and is a separate thing entirely. If you've moved your Documents folder to another drive — plenty of us have, for space — the app.ini follows Documents, not the sim.

The sibling files people mix up

This is where most of the wasted evenings happen. Documents\iRacing holds several .ini files and they are not interchangeable.

core.ini exists twice. There's one in Documents\iRacing and one in your install directory, and they do different jobs. iRacing's IPv6 article is blunt about it when it tells you to create the install-directory version: "This is not the core.ini in the Documents/iRacing folder." If a forum post says "edit core.ini" without saying which, ignore it until you know.

The renderer files are where graphics live. rendererDX11Monitor.ini if you launch on a monitor, rendererDX11<VR runtime>.ini if you're in a headset. Your RAM and VRAM allocation — SysMemToUseMB and VidMemToUseMB, in a [Graphics Options] section — sits in those files, not in app.ini. I've seen that pair miscredited to app.ini repeatedly, including by search engines summarising iRacing's own docs.

And iRacing muddied this themselves. The 2026 Season 3 notes say, word for word:

For OpenXR, added an app.ini file setting "ResolutionScalePct" to [OpenXR] section of rendererDX11OpenXR.ini.

An "app.ini file setting" that goes in a different file. I'd rather flag that than pretend the documentation is tidy. If you're tuning VR resolution, you want the renderer file — the wider picture is in my iRacing VR guide.

There's one genuinely useful consequence of the split: the renderer files have a documented recovery path. Delete rendererDX11Oculus.ini (or whichever matches your device), relaunch, and iRacing rebuilds it from your current settings. app.ini has no equivalent published reset procedure. That asymmetry is exactly why the next section matters.

The four rules for editing it

1. Close the sim first. iRacing's own instruction is to edit the file "while the simulation is not running." This is the big one. The sim writes its own state back out, so if it's open when you save, your edit gets overwritten by the sim's copy and you conclude the setting "doesn't work." It works. You were racing the sim to the disk and losing.

2. Copy the file before you touch it. Paste an app.ini.bak next to it. Thirty seconds, and it's your only reliable undo given there's no documented reset.

3. Don't rename it, don't move it. iRacing's guidance on the sibling renderer files is "Save the file without changing the filename or location" and the same logic applies here. Notepad is happy to save you an app.ini.txt if you're not paying attention. Turn on file extensions in Windows Explorer before you start.

4. Restart the sim to see the change. It's read at launch. Alt-tabbing back in does nothing.

Two syntax notes while you're in there. Sections are square-bracketed headers like [Misc] or [Force Feedback], and a key only counts if it's under the right one. Everything after a semicolon on a line is a comment — iRacing uses them to document values inline:

[Misc]
excludeIPv6OnFarms=                       ; Comma-separated list of 0 or more of farms to not race using IPv6: (apne1,apse2,euc1,sae1,use2,usw1)

Don't delete those comments. They're the only documentation some of these keys have.

The keys I'll actually vouch for

I'm deliberately not publishing a big table of app.ini keys. iRacing does not maintain a public reference for this file, which means every "complete app.ini guide" you find is somebody's copy of a decade-old forum dump, and inventing plausible-looking keys is the exact failure mode I want to avoid. Here are the ones with a traceable source.

[Misc] excludeIPv6OnFarms= — documented properly by iRacing. Comma-separated race farms you want to keep off IPv6. As of August 2025 the prefixes are euc1 Frankfurt, use2 US-east, usw1 US-west, sae1 São Paulo, apne1 Tokyo, apse2 Sydney. Useful if IPv6 is better to some farms and worse to others, which does happen.

[TrueForce] trueForceSetGain= — added in the 2025 Season 4 build (2025.09.08.02). Default 1 means iRacing forces your TrueForce/Wheel LFE gain to 100% every time the sim launches. Set it to 0 and your base-side value sticks. This is the fix for the "my FUL setting keeps resetting" complaint, and I've written up the per-brand Wheel LFE offsets that make it matter.

The [TrueForce] per-effect gains — the dB trims for engine, road texture, gear change and the rest. Note the section is named after Logitech's system regardless of what base you own; I unpicked that naming mess in Wheel LFE vs TrueForce vs FullForce.

[Force Feedback] loadFanatecAPI= and friends — the per-manufacturer switches that cut the direct API connection and drop you to generic FFB. Relevant if you're chasing the 360 Hz FFB mode.

[Force Feedback] resetWhenFFBLost= — resets the device when another application interrupts force feedback. Setting it to 0 is the standard fix when a third-party FFB tool keeps losing control on session change.

[SPCC] — the spotter section, which is what you're after if you're installing spotter packs.

If a key you found isn't in a release note or a support article, treat it as unverified. Try it, keep your backup, and don't build a settings sheet on it.

What survives a season update

Honestly: nobody outside iRacing can promise you this, and I'm not going to pretend otherwise. What I can show you is that keys do get added and removed, from iRacing's own notes.

Removed — 2025 Season 3 Patch 2:

Drive shaft effect has been turned off and removed from the app.ini file.

Removed — 2026 Season 3:

The display of far terrains may no longer be disabled in the ".ini" file. This was never graphically intensive.

Added — 2026 Season 3, where a launcher toggle now writes into the file for you:

An option has been added near the current networking option to enable IPv6 called "Use Anycast". This option is defaulted to "on" and enables the Anycast setting in the app.ini file.

And a nice illustration that the file and the menus interact — same build:

Updated AutoFuel to be auto-enabled when leaving the pits (if 'autoFuelDefaultEnable' is set) regardless of the 'autoResetPitBox' and 'autoResetFastRepair' settings in app.ini.

Practical takeaway: after every season build, open your backup alongside the live file and diff them. A key that quietly disappeared is not a bug you can fix by re-adding it — it's a feature iRacing removed, and the drive shaft line above is the perfect example. Anyone still telling you to tune a drive shaft channel is quoting advice from before June 2025.

Worth timing this, too. As I write, the current build is 2026 Season 3 and its patches. Season 4 is expected to go live around 8 September 2026, with the competitive season starting roughly a week later. If you're about to spend an evening in this file, either do it now and diff afterwards, or wait a week.

FAQ

Where is app.ini in iRacing? C:\Users\<your user>\Documents\iRacing\app.ini. That's your Documents folder, not the iRacing install directory. If you've relocated Documents to another drive, it moved with it.

Do I have to close iRacing before editing app.ini? Yes. iRacing's own instruction is to edit it while the simulation is not running. Edit it with the sim open and the sim will write its version back over yours when it closes.

How do I reset app.ini to default? There's no published reset procedure, which is why you copy the file before editing. The renderer .ini files can be deleted and rebuilt; app.ini can't be treated the same way. Keep a backup.

Will a season update wipe my app.ini changes? Not wholesale, but individual keys have been removed by builds before — the drive shaft effect in 2025 Season 3 Patch 2, the far terrain toggle in 2026 Season 3. Diff your backup against the live file after each season build.

Why did my app.ini edit not do anything? Three usual suspects, in order: the sim was open when you saved, you didn't restart the sim afterwards, or the key is sitting under the wrong [Section] header. Also check Notepad didn't save it as app.ini.txt.

Is there a full list of app.ini settings? Not an official one. iRacing documents individual keys in release notes and support articles but publishes no complete reference. Any "full list" you find online is a community copy of a specific build, usually years old, and will contain keys that no longer exist.

Should I edit app.ini or use the menus? Menus first, always. Since the Options reshuffle a lot of what used to be file-only is now exposed in the UI — I mapped the current layout in the FFB and Haptics settings page guide. Go to the file for what the UI genuinely doesn't offer.