Benchmark Builder
Compare the real-world execution speed of two JavaScript snippets, run directly in your own browser.
Code you enter runs directly in your browser, just like typing it into the developer console - only run code you wrote or trust. Modern JS engines can also optimize away trivial loops, so results are most meaningful for realistic, non-trivial snippets.
Recommended Settings
Pro Tips
- •Each snippet is run once first to catch errors, then run repeatedly in a tight loop while measuring total elapsed time with the high-resolution Performance API
- •Results can vary between runs due to JIT compilation warmup, garbage collection, and other browser activity - run a benchmark a few times to see if the result is consistent
- •Very simple or side-effect-free code may be optimized away entirely by the JavaScript engine, producing misleadingly fast results - benchmark realistic code that does real work
- •This measures relative performance in your specific browser and hardware - results won't necessarily match a different browser, device, or JS engine
Most Popular
Most developers compare two different implementations of the same logic (like two ways to sort or deduplicate an array) at 100,000 iterations
When to Use This Tool
Measure which of two implementations of the same logic actually runs faster.
Verify that a proposed optimization actually improves performance before committing to it.
Experiment with how different code patterns affect real-world execution speed.
Get concrete numbers to resolve a disagreement about which approach is faster.
How It Works
Compile each snippet into a callable function and run it once to surface any errors immediately
Run the function repeatedly in a tight loop for your chosen iteration count, timing the total duration with the Performance API
Calculate operations per second from the total time and iteration count, and compare the two results
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Client-side JavaScript execution and the Performance API for optimal performance on modern browsers.
Open Source
Built with verified, open-source libraries. Fully transparent.
Frequently Asked Questions
Is it safe to run code here?
Code runs directly in your own browser tab, exactly like pasting it into the developer console - it never leaves your browser or affects anyone else. Only run code you wrote or trust, the same caution you'd use with any script.
Why do my results vary between runs?
JavaScript engines apply just-in-time compilation and optimization that can change performance characteristics between runs, and background browser activity or garbage collection can also introduce variance - run the benchmark multiple times for a more reliable picture.
Why did my snippet with no side effects run unrealistically fast?
JavaScript engines can detect when code's result is never used and optimize it away entirely (dead code elimination), producing a misleadingly fast result - make sure your snippet does something the engine can't optimize away, like accumulating a value.
Do results transfer to other browsers or devices?
No, results reflect your specific browser's JavaScript engine and your device's current performance - the same code can perform quite differently in a different browser or on different hardware.