Measure download and upload speed to gauge your bandwidth.
Measure network latency and jitter with repeated requests.
Press keys to check your keyboard and see key codes.
Click and move to check mouse buttons and scroll wheel.
Show pure colors and bars to check dead pixels and colors.
Check if your microphone captures sound with live level meter.
Test regular expressions with match, replace and count.
Validate and format JSON with clear error messages.
Percent-encode and decode URLs or text.
Remove duplicate lines and sort to clean text data.