How would you write differently to another audience, such as your best friend or a sister

Writing to an audience is different than writing to a loved one. First, I would make it formal. Usually, when people write to their best friend or sister, they’ll write causally. Next, I would make sure my writing can be understood universally. The writing must be understood by anyone and not be confusing. When writing to a loved one, I can make an inside joke or too, but I cannot do that with an audience. Therefore, I would change my writing by making it formal and universally understood.