ScreenCheckv1.0
motion
1–2 min
Client-Side Local

Refresh Rate Test

Measures browser animation frame intervals across hundreds of consecutive samples to calculate estimated display refresh rate (Hz), frame time jitter, minimum/maximum delta, and standard deviation.

Testing Instructions
  1. Keep this browser tab active and focused for consistent frame pacing.
  2. Allow the tool to gather at least 180 to 240 frame samples.
  3. Inspect the Estimated Refresh Rate, Average Frame Time, and Jitter metrics.
  4. Notice: JavaScript estimates effective VSync delivery inside the browser compositing pipeline; results can be affected by OS scaling, power-saving profiles, or multi-monitor setups.
Interaction Controls
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Motion Environment & VSync Validation

Live browser animation timing evaluation

Sampling Cadence (0/180)
Estimated Refresh Rate
Measuring...
Standard: ~60 Hz
Average Frame Time
16.67 ms
Jitter: ±0.00 ms
Frame Stability
Unstable
Confidence: 0%
Samples Collected
0
Late frames: 0
Browser Timing Limitation Note: JavaScript cannot directly read monitor hardware refresh rates or panel EDID data. This is an Estimated Refresh Rate calculated from browser compositing intervals. Results may be affected by OS window managers (DWM/Quartz), battery-saving profiles, background tabs, Variable Refresh Rate (VRR), and multi-monitor setups.
Frame-Time Telemetry
Pacing: High Variance
Estimated Hz
Sampling...
~60 Hz standard
Avg Frame Time
16.67 ms
Target: 16.67 ms
Jitter (StdDev)
±0.00 ms
Frame consistency
P95 Latency
16.67 ms
95% of frames below
Worst Spike
16.67 ms
0 late frames
Cadence Distribution & Statistical Intervals
Median Interval16.67 ms
Minimum Frame Time16.67 ms
Maximum Frame Time16.67 ms
P99 Latency (Worst 1%)16.67 ms
How refresh rate is estimated: Rather than relying on simple averages which can be distorted by single background spikes, ScreenCheck applies robust median filtering across hundreds of consecutive frames to accurately calculate your effective display VSync interval.

What This Test Checks

  • Effective browser animation frame delivery rate (requestAnimationFrame intervals).
  • Frame time jitter and standard deviation across hundreds of consecutive samples.
  • Alignment with standard display refresh rates: 60Hz, 75Hz, 120Hz, 144Hz, 165Hz, 240Hz, 360Hz.
  • Compositing stability and background window throttling impact.

How to Perform the Test

  • Keep this browser window active and in the foreground for at least 3 seconds.
  • Allow the sampler to accumulate at least 180 to 240 frames.
  • Check the Estimated Refresh Rate and Average Frame Time values.
  • If the rate is locked to 60Hz on a 120Hz/144Hz monitor, verify your OS display settings.

What to Look For

  • Steady frame intervals (e.g. 16.67ms for 60Hz, 8.33ms for 120Hz, 6.94ms for 144Hz).
  • Low jitter (standard deviation below 1.0 ms indicates smooth, stable frame pacing).
  • Low confidence or high jitter usually indicates background tasks or power-saving throttling.

Common Display Problems & Diagnostic Guidance

Monitor Set to 60Hz in Windows / macOS Settings

A very common issue is purchasing a 144Hz or 240Hz monitor but leaving the operating system display settings set to the 60Hz default. Check Windows Advanced Display Settings or macOS Displays.

Browser Hardware Acceleration Disabled

If hardware acceleration is turned off in Chrome, Edge, or Firefox settings, animation frames may cap at 60Hz or stutter severely due to CPU software rendering.

HDMI Cable Bandwidth Bottlenecks

Older HDMI 1.4 cables cannot carry 144Hz or 240Hz at 1440p or 4K resolutions. Use DisplayPort 1.4 or HDMI 2.1 cables for high-refresh rates.

Frequently Asked Questions

Can JavaScript directly read my monitor’s physical refresh rate?

No web browser API exists to read hardware EDID refresh rates directly. ScreenCheck measures high-resolution requestAnimationFrame intervals to accurately estimate your effective refresh rate.

Why does my 144Hz monitor show 143.9Hz or 144.1Hz?

Pixel clocks in graphics cards have slight timing variance (typically within 0.1%). Browser scheduling also introduces microsecond variations.