Understanding the result
The estimated refresh rate is calculated from the trimmed interdecile core (middle 80%) of high-resolution foreground animation-frame intervals. A result near 60, 120, 144, 165, or 240 Hz accurately reflects the active presentation frequency delivered by your browser and operating system compositor. Note that this test measures the live presentation rate of rendered browser frames; it does not directly query monitor firmware, DisplayPort link bandwidth, or GPU control panel settings.
How to use this tool
- Position this browser window on the specific monitor or screen you want to test.
- Keep the browser tab in the foreground throughout the measurement to prevent background throttling.
- Click 'Start Refresh Rate Test' to begin sampling high-resolution animation-frame intervals.
- Wait approximately 3 to 4 seconds while the test gathers hundreds of frame presentation cycles.
- Review your estimated refresh rate, frame time in milliseconds, and timing stability rating.
- Expand 'Measurement Details' to inspect jitter variation, dropped frame counts, and raw calculated Hz.
- Click 'View Motion Demo' to visually compare 30 FPS, 60 FPS, and high-refresh fluidity side by side.
How Browser Refresh Rate Measurement Works (requestAnimationFrame)
Modern web browsers coordinate rendering with display hardware through vertical synchronization (VSYNC) pulses. When you start the test, the browser triggers requestAnimationFrame callbacks aligned with each display refresh interval. By capturing hundreds of consecutive high-resolution timestamps via performance.now(), sorting the deltas, and trimming the top and bottom 10% outliers, DeviceTestRoom isolates the dominant presentation interval. This robust statistical median eliminates distortions caused by occasional dropped frames or background operating system scheduler interrupts, yielding an accurate reflection of the monitor's active presentation frequency.
Refresh Rate (Hz) vs Frame Rate (FPS): Why They Are Different
Refresh rate and frame rate represent two distinct stages of the visual pipeline. Refresh rate (measured in Hertz, Hz) is a hardware specification indicating how many times per second the physical monitor updates its pixel matrix (for example, 144 times each second on a 144 Hz panel). Frame rate (measured in Frames Per Second, FPS) measures how many distinct images your graphics card and application software produce each second. A video game might render 90 FPS on a 144 Hz monitor, meaning the monitor refreshes 144 times by repeating certain frames. Conversely, rendering 300 FPS on a 60 Hz monitor still only displays 60 physical updates each second, resulting in discarded frames or visual horizontal tearing.
What Frame Time Means (and Why It Is Not Input Lag)
Frame time represents the mathematical duration in milliseconds between consecutive screen presentation updates (calculated as 1000 / Hz). A standard 60 Hz monitor updates every 16.67 ms; a 120 Hz display updates every 8.33 ms; a 144 Hz display updates every 6.94 ms; a 240 Hz gaming monitor updates every 4.17 ms; and a 360 Hz esports screen updates every 2.78 ms. Shorter frame times ensure visual updates reach your eyes more frequently, creating smoother perceived motion. However, frame time must never be confused with input lag (the total latency from a mouse click to screen illumination) or pixel response time (how fast liquid crystals transition between gray shades).
Why a 144Hz, 165Hz, or 240Hz Monitor May Be Stuck at 60Hz
A frequent issue encountered by PC gamers is discovering that an expensive high-refresh monitor is operating at basic 60 Hz. When a monitor is connected for the first time, Windows and macOS almost universally default to 60 Hz to guarantee display compatibility. To enable high refresh rates, users must manually navigate to Windows Settings > System > Display > Advanced display, or macOS System Settings > Displays, and select 144 Hz or 240 Hz from the refresh rate dropdown. Additional common bottlenecks include: connecting through an older HDMI 1.2/1.4 cable instead of DisplayPort 1.4 or HDMI 2.1; plugging the cable into the motherboard video port instead of the discrete GPU; using an office USB-C hub capped at 60 Hz; or running with disabled browser hardware acceleration.
Multi-Monitor Setups and Mixed Refresh Rate Compositing
Operating multiple monitors with mismatched refresh rates (such as a 60 Hz secondary screen alongside a 165 Hz primary gaming monitor) introduces compositor challenges. In older operating systems, the desktop window manager frequently synchronized GPU output to the slowest connected monitor whenever hardware-accelerated media played on the secondary screen. While modern Windows 11 and macOS window managers handle mixed refresh rates far more gracefully, keeping your browser window completely contained on the high-refresh monitor ensures the compositor prioritizes that display's VSYNC clock.
Variable Refresh Rate (VRR), G-SYNC, FreeSync, and Adaptive-Sync
Traditional fixed-refresh monitors refresh at rigid, unchanging time intervals. When application frame rates drop below the display's fixed rate, traditional VSYNC introduces visible stutter or tearing. Variable Refresh Rate (VRR) technologies—including NVIDIA G-SYNC, AMD FreeSync, and VESA Adaptive-Sync—dynamically synchronize the monitor's refresh cycles directly with the GPU's frame generation speed. In a desktop browser environment displaying static content, VRR may allow the panel to drop into lower power-saving refresh brackets, which is why active foreground animation testing provides a reliable verification of the current presentation ceiling.
Smartphone and Tablet Adaptive Refresh (ProMotion and LTPO)
Modern flagship smartphones and tablets frequently feature high-refresh screens marketed as 120 Hz (such as Apple ProMotion or Samsung Dynamic AMOLED 2X). However, these mobile displays utilize Low-Temperature Polycrystalline Oxide (LTPO) backplanes that dynamically throttle refresh rates from 1 Hz up to 120 Hz to conserve battery. When viewing a static webpage without active finger contact or continuous scrolling, the mobile operating system throttles browser presentation to 60 Hz or lower. This is intentional power-saving engineering, not a defective panel or inaccurate manufacturer specification.
Hardware Acceleration, Remote Desktops, and Virtual Machines
Browser frame presentation relies directly on the browser's hardware-accelerated GPU compositor pipeline. If hardware acceleration is disabled in browser settings, rendering falls back to CPU software rasterization, which frequently caps animation frame delivery at 60 Hz with noticeable timing jitter. Furthermore, if you access a computer via Remote Desktop Protocol (RDP), Citrix, TeamViewer, or a Virtual Machine, the virtualized display driver limits presentation rates to bandwidth-conserving rates (typically 30 Hz or 60 Hz), completely bypassing the remote host's physical high-refresh display capabilities.
Troubleshooting
- Result shows ~60 Hz on a 144 Hz or 240 Hz monitor: Open Windows Settings > System > Display > Advanced display, or macOS System Settings > Displays, and confirm the refresh rate dropdown is explicitly set to 144 Hz or higher rather than the 60 Hz default.
- Result changes slightly between test runs (e.g., 143.8 Hz vs 144.1 Hz): Minor decimal fluctuations are normal. Web browsers measure intervals using microsecond-precision timestamps that reflect real-time operating system scheduler jitter and GPU frame pacing.
- The test paused or stopped with a warning: The test requires this tab to remain in the active foreground. If you switch tabs, minimize the window, or lock your screen, modern browsers throttle background timers to save battery.
- Laptop on battery power produces a lower Hz estimate: Many laptops automatically switch the display from 120Hz/144Hz down to 60Hz or enable Dynamic Refresh Rate (DRR) when unplugged to conserve battery life.
- Multi-monitor setup showing unexpected rate: If you have a 60 Hz display and a 144 Hz display connected, moving the window across screens or having hardware acceleration conflicts can cause the browser to sync to the slower monitor. Keep the window entirely on the high-refresh monitor.
- Motion comparison demo appears stuttery: Heavy background downloads, 3D applications, or power-saving browser modes can cause dropped frames. Close unnecessary background tabs and ensure hardware acceleration is enabled in browser settings.
- Smartphone or tablet advertises 120 Hz but tests at 60 Hz: Mobile devices with LTPO or ProMotion adaptive refresh dynamically reduce the screen refresh rate to 60 Hz or lower when viewing static web pages, only boosting to 120 Hz during continuous finger scrolling.
- Connected via docking station or HDMI adapter: Some basic USB-C hubs, HDMI 1.4 cables, or KVM switches are limited to 4K 30Hz or 1080p 60Hz. Verify that your cable and port support high-refresh DisplayPort Alt Mode or HDMI 2.0/2.1.
Browser and device limitations
This test measures browser presentation frame timing via requestAnimationFrame. While highly accurate for evaluating the real-world frame cadence delivered to your eyes, it cannot directly inspect monitor EDID hardware profiles, measure physical liquid crystal pixel response time (GtG), or determine display input lag without dedicated optical photodiode hardware.
Common questions
How do I test my monitor refresh rate?
Move this browser window to the screen you wish to check, click 'Start Refresh Rate Test', and keep the page open in the foreground for four seconds. The tool captures hundreds of animation frame intervals to calculate your current display presentation rate.
Is this online refresh rate test accurate?
Yes, for measuring actual browser presentation timing. Modern browsers synchronize requestAnimationFrame callbacks with the display's vertical refresh cycle (VSYNC). While it does not query monitor firmware directly, it accurately reflects the real-world frame rate delivered to your screen.
Why does my 144 Hz or 240 Hz monitor show 60 Hz?
By default, Windows and macOS often set new high-refresh displays to 60 Hz. To fix this, open your operating system's Display Settings, select your monitor, and choose 144 Hz or 240 Hz under Advanced Display / Refresh Rate. Also ensure you are using a DisplayPort or high-speed HDMI cable.
What is the difference between refresh rate (Hz) and frame rate (FPS)?
Refresh rate (measured in Hz) is how many times per second your physical monitor refreshes its image. Frame rate (measured in FPS) is how many rendered frames your graphics card or application produces per second. A game might output 90 FPS on a 144 Hz monitor, or 200 FPS on a 60 Hz monitor.
What does frame time mean?
Frame time is the time in milliseconds between consecutive screen updates (calculated as 1000 / Hz). For example, 60 Hz has a 16.67 ms frame time, 120 Hz is 8.33 ms, 144 Hz is 6.94 ms, and 240 Hz is 4.17 ms. Lower frame times yield smoother, more responsive visual motion.
Can I test refresh rate on a smartphone or tablet?
Yes. The test works on iPhone, iPad, Android, and mobile browsers. Keep in mind that mobile screens with adaptive refresh (such as ProMotion or LTPO displays) dynamically throttle down to 60 Hz or lower when static, and ramp up to 120 Hz during active touch or scroll interactions.
Does having multiple monitors affect the refresh rate test?
It can. If you have monitors with different refresh rates (such as a 60 Hz secondary screen and a 144 Hz primary gaming screen), some operating system compositors synchronize browser windows based on the slowest display or window placement. Always keep the window entirely on the high-refresh monitor.
Can JavaScript or web browsers read the monitor's exact hardware model and maximum Hz?
No. For security, privacy, and sandboxing reasons, web browsers do not expose raw monitor serial numbers, EDID hardware tables, or factory maximum capabilities. The browser test accurately measures the actual frame delivery timing produced by the operating system and GPU compositor for that browser window.
