Both “useful to” and “useful for” are grammatically correct and can often be used interchangeably. “Useful to” is better suited in a more specific case, i.e., “It was useful to me”. “Useful for” is used in more general terms, i.e., “It was useful for our research”.

The phrase “useful to” emphasizes the personalized benefits or applications that are of direct relevance to the individual or situation at hand. “Useful for” merely suggests a general usefulness that may span various settings, individuals, or objectives.

Use “to” when the reason or purpose is a verb. Use “for” when the reason or purpose is a noun. That’s all!

When highlighting the importance of something, both to or for could be used. But there’s a slight difference in meaning or focus: Important to me = indicates personal or sentimental value; something precious to you Important for me = indicates or focuses on the benefit of something.