Browser Timer Test

A tool for measuring the accuracy and reliability of JavaScript timers (setTimeout and setInterval) across different browsers.

Overview

Browser Timer Test provides (hopefully) detailed measurements of how accurately browsers implement JavaScript timing functions. It runs a series of tests with both short (50ms) and long (10s) durations using both setTimeout and setInterval, then provides statistical analysis of the results.

Features

• Tests both setTimeout and setInterval
• Measures short (50ms) and long (10s) duration timers
• Provides statistical analysis (average, min, max, standard deviation)
• Shows real-time progress of tests
• Detects browser and operating system information
• Exports raw test data as JSON

How to run

Clone the repository and open the browser-timer-test directory. Ensure you have Node.js installed.

1. Run npm install to install dependencies
2. Run npm run start to serve the website on port 8080.
3. Open your browser and go to http://localhost:8080

You can also export the raw data as JSON by clicking the "Export Raw Data" button.

Test Details

• Short Timeout Test: 100 trials of 50ms timeouts
• Short Interval Test: 100 cycles of 50ms intervals
• Long Timeout Test: 5 trials of 10-second timeouts
• Long Interval Test: 5 cycles of 10-second intervals

Understanding the Results

• Drift: The difference between expected and actual time (in milliseconds)
• Positive drift: Timer fired later than expected
• Negative drift: Timer fired earlier than expected
• Higher standard deviation: Less consistent timing

Why This Matters

JavaScript timers are not guaranteed to be precise. Browsers implement them differently, and factors like system load, background tabs, and power-saving features can affect their accuracy. Understanding these limitations is crucial when building time-sensitive web applications.

Acknowledgements (OSS)

• Bootstrap (Link): Licensed under MIT License
  • Copyright (c) 2011-2025 The Bootstrap Authors
• Material Design Icons by Pictogrammers (GitHub): Icons licensed under Apache License 2.0
• ts-pattern (Link): Licensed under MIT License
  • Copyright (c) 2021 Gabriel Vergnaud
• Webpack (Link): Licensed under MIT License
  • Copyright JS Foundation and other contributors

Copyright (c) 2025 Diego Perez (iKarTehFox)