The Overzealous Editor
macOS includes a system-wide autocorrect engine designed to catch typos and enforce standard grammar rules across almost all native applications (like Mail, Messages, and Notes). One of its primary functions is auto-capitalization, which automatically capitalizes the first letter of a new sentence or the first letter of recognized proper nouns. While helpful for standard correspondence, this feature can be incredibly frustrating if you are writing code snippets in a plain text editor, formatting specific commands that require lowercase syntax, or simply prefer a stylized, all-lowercase approach to informal messaging. The OS will stubbornly override your keystrokes, forcing you to go back and manually downcase letters.
Disabling Auto-Capitalization in Keyboard Settings
To regain strict control over your typing and stop macOS from automatically correcting capitalization across the operating system, you must disable the feature in your Keyboard settings.
Click the Apple logo in the top-left corner of your screen and select System Settings (or System Preferences on older versions of macOS). Scroll down the left sidebar and click on Keyboard. In the main window, look for the “Text Input” section and click the Edit button next to “Input Sources” (or simply look for the “Text” tab if you are on an older macOS). Look through the list of spelling and grammar toggles. Find the option labeled Capitalize words automatically. Click the toggle switch next to it to turn it to the Off position (the switch will turn gray). The change takes effect immediately across all native apps that utilize the macOS text engine, ensuring your lowercase letters remain exactly as you type them.