If your PC feels sluggish, the program you installed to keep it safe could be doing more harm than good.
Background / Overview
Antivirus software is one of the first things many people install on a new Windows PC. It promises constant protection — real‑time scanning, web and download filtering, ransomware shields — and for the most part it delivers useful defenses. But over the last decade security suites have grown into full ecosystems: VPNs, password managers, system optimizers, browser extensions, “secure” browsers and more. Those extras bring value for some users, but they also introduce additional background processes, scheduled tasks, and network traffic that compete with the apps you actually want to run.
The result is an uncomfortable irony: the suite meant to protect your system can also be a major friction point for everything from web browsing to video editing and gaming. Independent lab testing and hands‑on reviews consistently show wide variation between products when it comes to performance impact. At the same time, the built‑in Windows protection — Microsoft Defender — has matured into a capable, low‑overhead default that, in many real‑world scenarios, delivers comparable protection without the extras that eat system resources.
This article walks through how antivirus slows a PC, how to verify whether it’s your bottleneck, practical tuning steps to regain performance while preserving safety, and a realistic decision framework for whether to keep a third‑party suite or rely on Windows built‑in defenses.
How antivirus software slows your PC
Real‑time scanning: always on, always watching
Most antivirus products offer
real‑time protection, which inspects files as they are opened, executed, copied, downloaded or modified. That requires the security engine to hook into file I/O and process execution paths, scanning newly accessed objects on the fly.
- That means every program launch, every document open, and every file copy can trigger checks.
- On low‑end systems or with heavy disk activity, on‑access scanning can noticeably increase latency for application startups, file transfers and installs.
Real‑time protection is essential to stop many common threats, but the scanning layer is also the most likely source of constant overhead.
Scheduled and full scans: spikes in resource usage
Antivirus suites also run scheduled scans. A quick scan checks critical areas and is usually light; a full system scan is thorough and can spike CPU, disk and memory use while it runs. Reported scan load varies wildly by product, scan depth, and hardware; internal tests and reviews have recorded anything from modest CPU use during full scans to sustained spikes that consume the majority of a CPU on older machines.
What that means in practice: if a full scan kicks off while you’re gaming or rendering video, expect stutters, frame drops and elongated job completion times.
Bundled extras: the hidden processes
Modern security suites rarely stop at malware detection. Vendors bundle VPNs, password managers, system tune‑ups, browser extensions, and even their own web browser. Each extra creates at least one background process, scheduled job, service, or kernel hook.
- Extra processes increase RAM footprint and add CPU and disk contention.
- Browser extensions add runtime checks and network redirection that can slow web pages.
- Built‑in VPNs can reroute and inspect traffic, adding latency and CPU work.
The more features a suite packs, the greater the chance it will tax your system at times you don’t expect.
Conflicting priorities during heavy workloads
When you start a resource‑intensive application — a modern game, a DAW, or a video encoder — both the app and the security suite may try to use CPU, disk I/O and memory. Unless the antivirus provides a true low‑interference mode, you’ll likely see both applications fight briefly for headroom, which manifests as higher latency, reduced framerate, or slower responsiveness.
Verify first: is the antivirus really the problem?
Before you start changing settings or uninstalling anything, confirm the antivirus is the bottleneck. These are the steps to run a quick, safe diagnosis.
Quick Task Manager check
- Press Ctrl + Shift + Esc to open Task Manager.
- Click the Processes tab and sort by CPU, Memory or Disk.
- Look for processes from your antivirus vendor and note their usage over several minutes.
If the antivirus process regularly shows double‑digit percentages of CPU or persistent high disk usage while your system is idle, that’s a red flag.
Reproduce the slowdown safely
- Save your work and disconnect from the internet if you feel uncomfortable disabling protection temporarily.
- Use the antivirus app’s interface to pause real‑time protection (most apps allow a temporary pause).
- Run the application or game that was lagging and observe performance.
If responsiveness improves noticeably while protection is paused, the antivirus was almost certainly contributing to the slowdown. Re‑enable protection immediately after the test.
Important safety note:
Never run a test with protection paused if you plan to download or browse unknown sites. Keep the test contained and re‑enable protection as soon as you’ve finished.
Try a clean boot
A clean boot starts Windows with a minimal set of drivers and startup programs and helps isolate whether the AV or another background app is the issue.
- Open System Configuration (msconfig).
- On the Services tab, check “Hide all Microsoft services,” then disable remaining third‑party services.
- Reboot and test the performance scenario again.
If performance improves in a clean boot and you see your antivirus among the disabled services, it’s likely implicated.
How to tune your antivirus without sacrificing protection
You don’t have to choose between security and performance. Many targeted changes reduce overhead and keep meaningful defenses intact.
1) Schedule full scans for idle hours
Change scan schedules so full system scans run late at night or during times the PC is usually idle. Quick scans and real‑time protection can stay enabled during the day.
- Most security suites let you define scan windows and CPU/disk throttling levels.
- Use scan throttling (if provided) to limit the number of cores or I/O the scan uses.
This prevents surprise slowdowns while you’re working or gaming.
2) Use gaming/performance mode
Many vendors offer a
Gaming Mode,
Silent Mode, or
Performance Mode that suspends nonessential background tasks while a full‑screen app is active.
- Enable that mode for games and professional apps.
- Confirm in the suite’s settings what it suspends — ideally it pauses scheduled scans and heavy update tasks, but leaves real‑time protection on.
If your suite lacks one, you can often create a Windows Focus Assist or power plan profile for similar outcomes.
3) Disable or uninstall unnecessary extras
Audit the bundled features and disable those you don’t need:
- VPNs: useful for travel and public Wi‑Fi, but they run continuously and add latency. Use a dedicated VPN app when needed rather than keeping the AV VPN always on.
- Password manager: standalone password managers usually offer better cross‑platform features and less integration overhead.
- Browser extensions and vendor browsers: uninstall or disable unless you actively use them.
Less running software equals fewer background threads competing for resources.
4) Apply exclusions carefully
Add targeted exclusions for folders or file types that are safe but performance‑sensitive:
- Game installations, large media directories, virtual machine disks, or development build directories can be excluded from real‑time scanning.
- Prefer folder or file‑type exclusions rather than excluding entire drives.
Caution: exclusions widen the attack surface. Only exclude directories you manage and trust, and keep exclusions minimal and well documented.
5) Tune scan depth and heuristics
Some suites let you adjust heuristic sensitivity and the depth of archive or nested archive scanning.
- Reduce archival depth for large compressed archives you frequently extract.
- Keep behavioral heuristics enabled — they’re vital for zero‑day protection — but lower heuristic aggressiveness only if you receive excessive false positives.
6) Limit auto‑start processes
Many suites install helper apps that start with Windows for features like software updates or VPN auto‑connect. Disable auto‑start for components you don’t need.
When to consider switching to Microsoft Defender
Microsoft Defender (the built‑in Windows Security suite) has evolved into a robust default option. Independent testing labs have repeatedly shown Defender to be competitive on protection and light on system impact. Its deep Windows integration lets it operate with minimal overhead, and it turns itself off automatically if a third‑party antivirus is installed, avoiding conflicts.
Consider Defender if:
- You use your PC primarily for browsing, streaming, document work, and casual gaming.
- You don’t need the VPN/password manager/system‑optimizer extras bundled with third‑party suites.
- You run a modern Windows 10 or Windows 11 device where Defender’s exploit mitigation features (ASR rules, tamper protection, controlled folder access) are available.
If you switch to Defender, make sure to harden it properly:
- Turn on Tamper Protection to prevent malware or unauthorized users from disabling Defender settings.
- Enable Cloud‑delivered protection and automatic sample submission to improve detection of new threats.
- Activate Controlled Folder Access (ransomware protection) and configure trusted apps.
- Keep Windows updated and use the built‑in firewall and browser protections such as SmartScreen.
For users with specialized security needs — corporate endpoints, extreme threat models, or advanced privacy requirements — third‑party suites or managed endpoint products may still be the better choice.
Risks and trade‑offs: what you give up when you strip back protection
Performance tuning and switching to lighter protection have trade‑offs you must accept.
- Disabling extras like VPNs or password managers removes convenience and potentially lowers privacy in certain scenarios (e.g., public Wi‑Fi).
- Adding exclusions increases risk if you misidentify an untrusted folder as safe.
- Temporarily pausing real‑time protection leaves you exposed; do tests offline or immediately reconnect protection.
- Built‑in protection like Defender is excellent for general use, but in some lab tests certain third‑party products still edge it out in protection or add enterprise‑grade features such as centralized management, sandboxing, or data loss prevention.
Make decisions with context: a home user who primarily streams and browses likely needs different protection than someone who regularly downloads code or deals with sensitive client data.
A practical checklist: speed vs. safety decisions you can make in 30 minutes
Use this checklist to get performance without abandoning safety. Each item takes only a few minutes.
- Open Task Manager and observe AV process resource use for 5 minutes.
- Pause real‑time protection (safely) and test the slow scenario for 2–3 minutes; re‑enable immediately.
- In the antivirus app:
- Reschedule full scans to late night.
- Enable gaming/performance mode if available.
- Turn off nonessential features (VPN, browser extensions, software updater).
- Add exclusions for large game or media folders (keep them minimal and documented).
- If switching to Defender:
- Uninstall the third‑party AV via Control Panel > Programs and Features (do not just disable).
- Confirm Windows Security shows “Virus & threat protection — On”.
- Enable Tamper Protection, Cloud‑delivered protection, and Controlled Folder Access.
- Reboot and run a short performance test or play the game to confirm improvements.
For power users and administrators
If you manage multiple machines or run workstations with high security requirements, blanket removal of third‑party AV is not a simple solution.
- Enterprise and IT environments commonly use centralized endpoint detection and response (EDR) and configuration management that depend on specific vendors.
- Group Policy and management platforms (Intune, SCCM, third‑party consoles) may enforce baseline AV and firewall settings for compliance. Removing mandated AV on a managed device can put you out of compliance and open you to risk.
- For advanced workflows, use solutions that offer per‑process throttling, curated exclusion lists, and centralized policies to balance performance with protection.
The bottom line: tune, don’t panic — but don’t ignore trade‑offs
Antivirus software can — and sometimes does — slow your PC, especially when full scans or bundled features run at inopportune times. But the solution isn’t reflexive removal; it’s deliberate tuning based on measured evidence.
- Start by verifying whether the AV is the bottleneck using Task Manager and controlled tests.
- Use scheduling, gaming/performance modes, and careful exclusions to reduce impact while retaining core defenses.
- Audit bundled extras and remove or disable those you don’t use.
- For many users, Microsoft Defender is a strong, lightweight default that frees system resources without a dramatic loss in protection, provided you enable its advanced features like tamper protection and ransomware shields.
- For enterprise or high‑risk users, retain purpose‑built security tooling and use management controls to minimize performance damage.
Security is a balance between protection and usability. With a few targeted adjustments you can usually regain responsiveness without leaving your PC exposed — and in the process you may discover that less software running in the background is the simplest route to a faster, more reliable machine.
In short: don’t assume your antivirus is innocent; measure it. If it’s the problem, tune before you toss — and if you do move to the lighter, built‑in option, harden it first so performance gains don’t become security losses.
Source: MakeUseOf
Your antivirus is probably slowing your PC more than protecting it