When should I replace my MacBook battery?

Replace it when the battery swells or when you can’t get through a normal workday without plugging in. The real signs are a trackpad clicking weirdly, a slightly bulged case, or needing the charger everywhere. Don’t wait for swelling to get bad—if the trackpad clicks unevenly or the bottom case won’t sit flat, stop charging and get to a repair shop. Apple’s battery health percentage is a rough guideline, not a rule.