Tools
Benchmark Builder
The benchmark tool lets you measure how fast JavaScript code runs in your browser. You can define test cases and run them for a configurable number of iterations to get reliable performance data. Results are shown as operations per second, making it easy to compare different implementations.
What is the Benchmark Tool?
The benchmark tool is a browser-based JavaScript performance measurement utility. It allows developers to run arbitrary code snippets for many iterations and measures how many operations per second can be completed. This is useful for comparing two algorithms, identifying bottlenecks, or verifying that an optimization actually improves speed. Results are shown with statistical context to account for runtime variance. Unlike server-side profilers, this tool measures real execution speed in the user's actual browser environment.
How does it work?
You enter one or more JavaScript snippets as test cases. The tool runs each snippet repeatedly in a tight loop and measures elapsed time using high-resolution performance APIs. After each run, it calculates the average duration and derives operations per second. The environment is warmed up before measurement to reduce JIT compilation noise. Multiple runs can be averaged to improve accuracy.
Typical Use Cases
- Comparing two sorting algorithm implementations
- Measuring DOM manipulation performance
- Evaluating string processing speed across different approaches
- Verifying that a refactored function is not slower than the original
Step-by-step Guide
- Step 1: Enter your JavaScript code snippet into the test case editor.
- Step 2: Set the number of iterations for the benchmark run.
- Step 3: Click Run to execute the benchmark in your browser.
- Step 4: Review the operations-per-second result and compare against other test cases.
Tips & Notes
- Always warm up the benchmark by running it once before recording results.
- Keep test cases isolated — avoid shared mutable state between snippets.
- Run benchmarks in an idle browser tab to reduce interference from other scripts.
Frequently Asked Questions
Why do benchmark results vary between runs?
JavaScript engines use just-in-time compilation, garbage collection, and CPU scheduling, all of which introduce variance. Running more iterations and averaging results reduces this noise.
Can I benchmark async code?
Async benchmarks require special handling because timing must account for promise resolution. Synchronous code is best suited for this type of microbenchmark tool.
Benchmark Builder
Compare the execution speed of multiple JavaScript snippets — with ops/s, time per iteration, and relative performance evaluation.
Open Tool