The Language Confusion
Google Docs is deeply integrated with your primary Google Account settings. Often, Docs will attempt to automatically detect the language you are typing in and adjust its internal dictionary and spellchecker accordingly. However, if you are a bilingual user frequently mixing two languages (like English and Spanish) in the same document, or if your overall Google Account language differs from the one you are currently typing in, Docs can become confused. It might automatically change the document’s recognized language halfway through a paragraph, causing every correctly spelled word to suddenly become underlined in red.
Locking the Document Language
To maintain consistent spellchecking and stop Google Docs from automatically changing the recognized language based on your Google Account defaults or mixed typing, you must explicitly set the language for the specific document.
Open the problematic Google Docs document. First, press Ctrl + A (or Command + A on a Mac) to highlight all the text currently in the document. This is a crucial step; if you do not highlight the text, the change may only apply to the next word you type. With the text highlighted, navigate to the top menu bar and click on File. Scroll down the drop-down menu and hover your cursor over Language. A large secondary menu will appear listing dozens of languages. Scroll through this list and click explicitly on the language you want to enforce (e.g., “English (United Kingdom)”). Docs will now lock that language in for the highlighted text and all future text you type in that specific document.