A balanced binary tree is a binary tree in which the depth of the two subtrees of every node differ by 1 or less. or we can say

```
public static int getHeight(TreeNode root) {
if (root == null) {
return 0;
}
return Math.max(getHeight(root.left), getHeight(root.right)) + 1;
}
public static boolean isBalanced(TreeNode root) {
if (root == null) {
return true;
}
int heightDiff = getHeight(root.left) - getHeight(root.right);
if (Math.abs(heightDiff) > 1) {
return false;
}
else {
return isBalanced(root.left) && isBalanced(root.right);
}
}
```