The Overzealous Shift Key
macOS includes a system-wide text input feature that automatically capitalises the first letter of every new sentence you type. After you type a full stop, question mark, or exclamation mark followed by a space, the next character is silently converted to uppercase. While this is a helpful convenience for casual emails and messages, it is a persistent source of frustration for developers writing code comments, data entry specialists typing product codes that must remain lowercase, and creative writers who deliberately use unconventional capitalisation for stylistic effect. The auto-capitalisation occurs across virtually every text input field on the system, from TextEdit and Notes to Safari form fields and third-party applications.
Disabling Automatic Capitalisation
To stop macOS from automatically capitalising the first letter of every sentence you type, you must disable the feature in the system Keyboard settings.
Click the Apple Logo in the top-left corner and select System Settings. In the left-hand sidebar, click on Keyboard. Scroll down to the “Text Input” section and click the Edit… button next to “Input Sources” (on older macOS versions, navigate to System Preferences > Keyboard > Text). In the text input settings panel, look for a toggle or checkbox labelled Capitalise words automatically. Turn this off or uncheck it. While you are in this panel, you may also want to disable Correct spelling automatically and Add full stop with double-space if those features are also interfering with your typing. Click Done to save. The change takes effect immediately across all applications. Note that some individual apps (like Pages or Keynote) may have their own capitalisation setting under Edit > Substitutions > Capitalization; ensure that is also unchecked for full coverage.