The Forced Capitalization
macOS borrows several text-editing features from its mobile counterpart, iOS, to create a unified ecosystem. One of the most prominent is automatic capitalization. By default, the operating system monitors your keystrokes and instantly capitalizes the first letter of any word you type immediately following a period, exclamation point, or question mark. While helpful for casual emails or general word processing, this is a massive hindrance for programmers typing code (where case sensitivity is critical), writers drafting stylized poetry, or anyone entering highly specific, lowercase terminal commands or usernames into web forms.
Disabling the Global Autocorrect
To regain complete manual control over the casing of your text and stop macOS from automatically capitalizing the first letter of sentences or words, you must disable the global keyboard correction settings.
Click the Apple logo in the extreme top-left corner of your screen and select System Settings. In the left-hand navigation sidebar, scroll down and click on Keyboard. On the right-hand panel, under the “Text Input” section, locate your primary input source (usually your language keyboard) and click the Edit… button next to it. A new dialogue window will appear. Look down the list of options for the toggle explicitly named Capitalize words automatically. If your Mac has been changing your text, this switch will be active. Click the toggle to turn it Off. Click Done. The change takes effect immediately across all native macOS applications; your letters will only be capitalized when you physically hold down the Shift key.