Windows Fast Startup is a hybrid boot feature designed to reduce boot time and help your PC start up more quickly. It’s a combination of traditional shutdown with hibernation technology help reduce boot times, especially on low-end devices with HDDs. First introduced in Windows 8 and refined in Windows 10 and 11, this feature saves the operating system’s state, including the Windows kernel and drivers, to a hibernation file (hiberfil.sys) instead of performing a complete shutdown. So, when you boot up the system next time, Windows simply reloads the saved system state instead of starting everything from scratch. In this article, we’ll explain what Fast Startup is, how it works, its pros and cons, and how to enable or disable Fast Startup in Windows 11 for the best performance and stability.
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What Is Fast Startup in Windows 11?
Fast Startup is a hybrid power feature on Windows PC designed to reduce the time it takes for a computer to start after shutdown. Unlike traditional boot processes that load all system components from scratch, Fast Startup loads a pre-saved system state stored in the hibernation file (hiberfil.sys). This innovative approach bridges the gap between a full shutdown and hibernation mode, offers faster boot times while maintaining the appearance of a complete shutdown.
The feature operates through the Advanced Configuration and Power Interface (ACPI) power states. Instead of entering the S5 power state (complete shutdown), Fast Startup enables the system to enter a hybrid state where user sessions are closed but the Windows kernel remains in hibernation. This stored kernel state enables rapid system initialization during the next boot cycle.
- S0 (Working State): Computer is fully powered on and operational
- S1-S3 (Sleep States): Various levels of sleep with different power consumption levels
- S4 (Hibernation): System appears off but hibernation file preserves the complete system state
- S5 (Soft Off): Complete shutdown with no saved state; full reboot required
- G3 (Mechanical Off): Zero power consumption; completely powered down
Fast Startup operates in a hybrid state between S4 and S5, utilizing hibernation technology while appearing as a shutdown.
How Fast Startup Works
When Fast Startup is enabled, the system performs a hybrid shutdown. It closes all applications and logs off users, similar to a normal shutdown, but instead of fully powering down, it saves the state of the Windows kernel and loaded drivers to a hibernation file (hiberfil.sys) on the hard drive.
Upon the next startup, the system reads this saved hibernation file, reloads the kernel and drivers from it, and quickly delivers the user to the login screen. This results in a significantly faster boot process, especially noticeable on older hardware or systems with traditional hard disk drives (HDDs).
When you shut down your PC:
- Windows closes all running apps and logs off user accounts.
- Instead of completely shutting down, the kernel session and device drivers are written to a file named hiberfil.sys (located on your system drive).
When you power on your PC:
- Windows reads this hibernation file and restores the kernel session from disk into memory.
- Since system drivers and services are already loaded, your desktop appears faster.
Advantages of Windows Fast Startup
The Fast Startup feature provides several noticeable benefits, especially for modern SSD-based systems.
- Faster Boot Times: This is the main advantage, your computer starts significantly faster because it restores a pre-saved kernel state instead of initializing all system components from scratch. According to Microsoft, Fast Startup can reduce boot time by 30-70% compared to traditional cold boots.
- Improved Battery Life on Laptops: For laptop users, Fast Startup extends battery life because less energy is required to boot the system from a hibernated kernel state compared to a full initialization. This energy efficiency makes it especially valuable for mobile computing scenarios where power conservation is critical.
- Ideal for Daily Users: If you shut down your PC daily, Fast Startup helps save time each time you power it back on, making it a good fit for home and office users.
- Reduced Wear on Hardware: Because fewer components undergo full initialization cycles, there is theoretically reduced wear on hardware components during startup. This can potentially extend the lifespan of system components, particularly mechanical hard drives.
Disadvantages of Fast Startup
You can consider Fast Startup as a great option to make Windows startup very fast. But there are some Disadvantages of Fast Startup, which force you to disable this feature.
- Issues with Dual-Boot Systems: For systems configured to dual-boot with other operating systems (such as Linux), Fast Startup causes serious compatibility problems. When Windows doesn’t fully release file system access during shutdown, the other operating system may encounter locked partitions, file system corruption, or inability to access shared drives.
- Interference with Windows Updates: Some updates require a full shutdown and startup cycle. With Fast Startup enabled, Windows might not install certain updates properly until you manually restart your system.
- BIOS/UEFI Access Problems: With Fast Startup enabled, pressing function keys (like F2, F12, or Del) at boot may not work properly because Windows doesn’t perform a full hardware initialization.
- Possible Drive Locking and File Access Errors: Fast Startup can cause issues if you use multiple drives or perform file transfers between systems, as some drives may remain in a “locked” state.
- Storage Space Consumption: The hibernation file (hiberfil.sys) consumes significant disk space, typically sized at 40-75% of installed RAM. On systems with limited storage capacity, this can become problematic.
Hibernate Vs Fast Startup
Fast Startup is different from the regular hibernation feature. Fast Startup saves the freshly started state of Windows. Meanwhile, the Hibernate option saves everything, including the current state, logged-in users, or open files, folders & applications. If you want to get back the exact state when you left your work, Hibernate is a great option but it takes longer to boot up.
How to Check If Fast Startup Is Enabled
By Default Fast Startup Feature is turned on on Windows 11 and 10 computers. You can check the same following steps below:
- Press Windows + R, type control, and press Enter to open the Control Panel.
- Click Hardware and Sound > Power Options > Choose what the power buttons do.
- Click Change settings that are currently unavailable (if required).
- Under Shutdown settings, check if Turn on fast startup (recommended) is selected.
If it’s checked, Fast Startup is currently enabled on your system.
However, if you experience problems such as missing drives, failed updates, or trouble entering BIOS, you may want to disable Fast Startup.
To Disable Fast Startup in Windows 11
- Open Control Panel and go to Hardware and Sound > Power Options.
- Click Choose what the power buttons do.
- Select Change settings that are currently unavailable.
- Uncheck Turn on fast startup (recommended).
- Click Save changes and restart your PC.
Your PC will now perform a complete shutdown each time, ensuring fresh hardware initialization.
Note: If there are only two options: Sleep and Lock, then it means Windows Hibernate isn’t enabled yet. In this case, you have to turn the Hibernate option first to enable Fast Startup.
You can also disable Fast Startup using the Command Prompt if the option is grayed out in Power Options.
- Press Windows + S, type cmd, and choose Run as administrator.
- Type command powercfg /h off and press Enter
- This command disables hibernation and Fast Startup together.
Note: Turning off hibernation also deletes the hiberfil.sys file, free up disk space, but disable related features like “Hibernate” mode.
Should I Keep Fast Startup Enabled or Disabled?
In most cases, keeping Fast Startup enabled is fine, especially for modern PCs with SSDs, but disabling it during troubleshooting or dual-boot situations is safer.
| Scenario | Recommendation |
| You use your PC for general tasks (home or office) | ✅ Keep Fast Startup enabled |
| You dual-boot Windows with another OS | ❌ Disable Fast Startup |
| You frequently install system updates or drivers | ⚙️ Disable temporarily |
| You troubleshoot BIOS/UEFI or hardware issues | ❌ Disable Fast Startup temporarily |
Fast Startup vs. Other Power Options
| Feature | Boot Time | Power Consumption | Data Preservation | Best For |
| Fast Startup | Fast | Minimal during shutdown | System kernel only | Quick daily boots |
| Hibernation | Medium | Zero during the off state | Complete session | Laptops saving battery |
| Sleep Mode | Instant | Low continuous power | Everything in RAM | Short breaks |
| Complete Shutdown | Slowest | Zero | Nothing preserved | Troubleshooting, updates |
| Restart | Medium | N/A | Nothing preserved | Installing updates |
Frequently Asked Questions
1. Does Fast Startup affect Restart?
No. The Restart option always performs a full system reboot, even if Fast Startup is enabled.
2. Is Fast Startup the same as Sleep or Hibernate?
No. Sleep keeps your session in RAM, while Hibernate saves it to disk. Fast Startup only hibernates system files (kernel session), not open programs.
3. Can Fast Startup cause any harm to hardware?
No, but it can sometimes prevent hardware from fully resetting between boots, leading to minor driver issues on some systems.
4. Will disabling Fast Startup slow down my computer?
Only the boot time is affected — your PC might take a few extra seconds to start, but overall performance remains the same.
5. How do I know if Fast Startup is working?
If your PC boots quickly after shutdown (within seconds), Fast Startup is likely enabled and functioning properly.
