Keyboard lag — where keystrokes appear with a noticeable delay — is caused by Bluetooth latency, high CPU load, or software interference. For Bluetooth keyboards: ensure the keyboard is paired directly (not through a hub), keep it within 3 feet of the receiver, and check the battery level. Low battery causes intermittent lag. For wired keyboards: unplug and reconnect, try a different USB port, and test in a text editor to rule out app-specific lag. Check CPU usage — if your system is overloaded, input processing slows down. On Windows, disable Filter Keys (Settings > Accessibility > Keyboard > Filter keys off) — this feature deliberately slows keystrokes. Disable Sticky Keys too if you didn't enable them intentionally. Close heavy background apps and test typing in Notepad. If lag only happens in specific apps (like browsers), disable extensions that might be intercepting keystrokes.