There were two main audiences for the Declaration of Independence. Those were the American colonists and the publics of other countries like France and even England.
The Declaration was written in part to rally public support for the Revolution within the colonies. With that in mind, it reminded people of all the things that the British government had done to offend them. This was meant to make them want to fight.
At the same time, the Declaration was meant to convince publics in other countries of the justice of the American cause. The Declaration is explicitly addressed to such people when it says that it is necessary to explain the American cause because of a "decent respect to the opinions of mankind." In other words, it is trying to convince all of "mankind" that the Americans are doing the right thing. This was important because, it was hoped, people in other countries would support what the colonies were doing and make it easier for them to succeed.
There were several audiences for the Declaration of Independence. Some audiences were intended, while some audiences, as it turned out, were unintended.
Clearly, the Declaration of Independence was aimed at the colonists. We needed to make our people aware that we had declared independence from Great Britain. They needed to know we were no longer loyal to Great Britain or being governed by them. They also needed to know that we likely would be fighting Great Britain for our independence. Finally, the Declaration of Independence let the colonists know that there are some rights that all people have.
The Declaration of Independence was also aimed at the British. They needed to know that we had declared our independence from them. They also needed to know why we did this. The Declaration of Independence let the British know that we wouldn’t be following their rules and regulations any longer.
The Declaration of Independence was also aimed at other countries. We needed to let other countries like Spain and France know that they should deal directly with us since we believed we no longer were under British control. These countries needed to know they could make deals with us and conduct other business with us.
There were some unintended audiences that the writers of the Declaration of Independence probably never thought they would have. Our Declaration of Independence served as a model for other countries that were having a revolution against their government. Countries like France and Vietnam used our Declaration of Independence as a model for their fight for freedom. Many Latin American countries also modeled their revolution after our revolution. They used our Declaration of Independence as a model. When Texas became independent from Mexican rule, the Texas Declaration of Independence was very similar to our Declaration of Independence.
There were many groups at which the Declaration of Independence was aimed. While the Declaration of Independence was clearly aimed at certain groups, it also impacted other groups that the writers probably didn’t have in mind at the time they wrote the document.