Yes, antivirus software can slow down your FPS, but how much depends entirely on what the antivirus is doing at that exact moment. A well-configured, modern antivirus running only its real-time protection in the background typically costs you somewhere between nothing and 3% of your frame rate. The same antivirus running a full system scan while you’re mid-match can drop your FPS by 15% or more. The gap between those two numbers is the whole story, and almost all of it comes down to configuration rather than which brand’s logo is on the box.
Why Antivirus Touches Your FPS at All
Every antivirus with real-time protection enabled hooks into the Windows file system so it can inspect files as they’re opened, written, or executed. Games are unusually demanding on this system compared to normal desktop use. A modern title can generate thousands of file access events per second while it streams textures, loads audio assets, writes save data, and reads shader caches. Each of those events is a potential interception point for a file system filter driver, and every interception adds a small amount of latency.
On its own, one intercepted file read costs a fraction of a millisecond. But when a game is hammering the disk during a level load, texture stream, or asset-heavy combat sequence, those fractions of a millisecond stack up into stutter and frame time spikes that are very noticeable even if your average FPS counter barely moves. This is why some players report “it feels laggy” even when overlay FPS counters look fine — the issue is often frame time consistency (1% lows), not the average number.
Real-Time Scanning vs. Scheduled Full Scans
These are two very different things, and lumping them together is where a lot of confusion comes from.
Real-time (on-access) scanning is always running in the background at a low intensity. It only inspects files as they’re touched, so its footprint during gameplay is generally small on a modern antivirus engine — independent lab testing puts the average impact from top-performing products at around 1 to 3% of FPS on a mid-to-high-end gaming PC, which is close to margin of error.
A scheduled full system scan is a completely different workload. It actively reads every file on your drive to check it against signatures and heuristics, competing directly with your game for CPU cycles and disk bandwidth. If a full scan kicks off while you’re playing, the performance hit can jump to 15 to 25% or worse, along with noticeable stutter, because now two demanding processes are fighting over the same disk I/O queue at the same time.
The practical takeaway: real-time protection is rarely your problem. An accidentally-scheduled full scan running at 8 p.m. instead of 3 a.m. usually is.
What Actually Causes the Worst Slowdowns
A few specific situations account for most of the antivirus-related FPS complaints reported by gamers:
- A full or quick scan overlapping with a play session. This is the single biggest cause of dramatic FPS drops, and it’s almost always a scheduling issue rather than a flaw in the software.
- Scanning inside your games folder repeatedly. Some antivirus products re-scan large executables and DLLs every time they’re launched or patched, which adds load time and occasional micro-stutter when new files are written mid-session (common with live-service games that patch on the fly).
- Heuristic/behavioral monitoring on anti-cheat and DRM processes. Kernel-level anti-cheat drivers (used by many competitive shooters) and antivirus real-time protection both hook deep into the OS, and the two occasionally step on each other, causing frame time spikes rather than a flat FPS reduction.
- Low-end or older hardware. On a CPU with fewer cores or a mechanical hard drive, the same scanning overhead that’s invisible on a modern rig becomes much more noticeable, because there’s less spare headroom to absorb it.
- Cloud lookup latency. Some antivirus engines send file hashes to the cloud for reputation checks before allowing execution. This is usually near-instant, but on a poor connection it can cause a brief hitch the first time a game or update file runs.
How Modern Antivirus “Game Mode” Features Work
Every major consumer antivirus vendor now ships some version of an automatic gaming/fullscreen mode, and they all work on roughly the same principle: detect that you’re in a fullscreen application, then suppress anything that would compete for resources or interrupt you.
- Avast and AVG’s Do Not Disturb Mode automatically detects when you open an application in fullscreen and adds it to a managed list, then silences notifications from Windows, the antivirus itself, and other apps whenever that app runs in fullscreen again.
- Norton’s gaming mode activates the moment you launch a game in fullscreen, auto-suppressing pop-ups, postponing scheduled scans, and blocking Windows notifications for the duration of the session.
- Bitdefender’s Autopilot/Game Profile uses behavioral heuristics plus a known-games list to detect fullscreen play, then disables alerts, promotional pop-ups, and Search Advisor, and postpones scheduled scans and updates until you’re done.
- ESET and Kaspersky’s Gamer Mode is enabled automatically whenever an application runs fullscreen, pausing scan and update tasks and suppressing notifications for as long as you’re playing.
The common thread across all of them: automatic fullscreen detection, postponed scans and updates, and suppressed pop-ups. None of these modes fully disable real-time protection — they reduce the parts of the software that compete for resources or interrupt you, while still keeping active threat protection running underneath.
How to Minimize Any Impact Yourself
You don’t have to rely purely on automatic detection. A few manual steps consistently reduce antivirus overhead during gaming:
- Add exclusions for your game folders and launchers. Excluding your Steam, Epic Games, or Battle.net install directories (and the game executables themselves) from real-time scanning stops the antivirus from repeatedly inspecting large, trusted files. Only do this for folders you trust — excluding random download directories defeats the purpose of having protection.
- Move scheduled scans to idle hours. Set full and quick scans to run at 3 a.m. or whenever your PC is typically idle, not “on startup” if you often start playing right after booting.
- Confirm game mode is actually triggering. Check your antivirus’s settings to see whether your specific game is recognized, especially for less mainstream titles or ones running in borderless windowed mode, which some engines detect less reliably than true exclusive fullscreen.
- Keep the antivirus updated. Engine updates frequently include performance optimizations, and older builds are disproportionately represented in FPS complaints.
- Avoid running two real-time scanners at once. Layering a second free antivirus on top of Windows Defender or your paid suite roughly doubles the file-interception overhead for no real security benefit, since Defender automatically steps back when another real-time AV is installed.
Does This Mean You Should Just Turn Antivirus Off?
No. Disabling real-time protection removes the one to three percent overhead but exposes you to malware that increasingly targets gamers specifically — fake cheat tools, cracked game installers, and pirated mod files are among the most common malware delivery vectors on PC. The performance cost of a modern, properly configured antivirus is small enough that trading it away for a marginal FPS gain is a poor bargain for almost every player. If you’re chasing every last frame for competitive play, the better move is exclusions and scan scheduling, not disabling protection outright.
Conclusion
Antivirus software does affect FPS, but the honest answer is “a little, if it’s set up right, and a lot if it isn’t.” Real-time protection from a modern, well-rated antivirus costs roughly 1 to 3% of your frame rate on a capable gaming PC — close to unnoticeable. The dramatic drops gamers complain about almost always trace back to a scheduled full scan running during a play session, repeated scanning of large trusted game files, or an outdated engine. Set your scans to run overnight, add your game folders as exclusions, confirm game mode is detecting your titles, and keep real-time protection on. That combination gets you protection and performance without meaningfully sacrificing either.