What Are JavaScript Key Codes?
JavaScript key codes are numeric values assigned to each key on a keyboard. When a user presses a key, the browser fires keyboard events (keydown, keyup, keypress) that contain properties like keyCode, key, code, and which. The keyCode property returns an integer (e.g., 13 for Enter, 27 for Escape), while event.key returns a string representation of the key ('Enter', 'Escape'). The event.code property represents the physical key on the keyboard regardless of layout, making it valuable for games and international keyboard support.
Why Key Code Lookup Matters for Developers
Building keyboard-driven interfaces requires knowing the exact codes for target keys. Whether you are implementing keyboard shortcuts (Ctrl+S to save), game controls (WASD movement), accessible navigation (Tab, Enter, Escape), or custom hotkeys, you need reliable key code references. Different browsers historically returned different keyCode values for some keys, making an interactive lookup tool essential for cross-browser testing and verification.
Key vs Code vs KeyCode Properties
The event.key property returns the logical meaning of the key (e.g., 'a' or 'A' depending on Shift state). The event.code property returns the physical key identifier (e.g., 'KeyA' regardless of keyboard layout or Shift state). The legacy event.keyCode returns a numeric integer that varies by key. Modern web development favors event.key and event.code over the deprecated keyCode, but legacy codebases still rely heavily on numeric key codes.
Best Practices for Keyboard Event Handling
Use event.key for character input detection and event.code for physical key position (important for games). Always handle both keydown and keyup for key combinations. Prevent default behavior carefully — blocking keyboard events can break accessibility. Test with different keyboard layouts (QWERTY, AZERTY, Dvorak) to ensure your key handling works internationally. Use this tool to verify key codes across browsers before hardcoding values into your application.
