The characters literally combine to mean “the truth (真相) is greatly (大) clear/white (白).” This paints a vivid picture of something that was once dark, murky, or hidden now being fully illuminated and easy for all to see.
The idiom 真相大白 reflects a deep-seated cultural value placed on justice (正义, zhèngyì) and the ultimate triumph of truth. In Chinese philosophy and storytelling, there is a strong belief that no matter how well a lie is crafted or how long a crime is hidden, the truth will eventually emerge. This concept is a cornerstone of historical epics, modern courtroom dramas, and even family disputes, providing a sense of moral and narrative satisfaction. A Westerner might compare 真相大白 to the phrase “the cat is out of the bag.” However, there's a key difference. “The cat is out of the bag” often implies a secret was revealed, perhaps accidentally, and doesn't necessarily have a positive or just outcome. 真相大白, on the other hand, is almost always positive. It signifies a resolution, a vindication of the innocent, and the clarification of a major, complex issue. It's less about a simple secret and more about the entire, often complicated, truth of a matter being definitively settled. It carries the weight of justice being served and order being restored.
真相大白 is a versatile idiom used in both formal and informal settings.
The connotation is consistently positive, as it represents a return to clarity and honesty.