Specifying an exact size is challenging because people have different screen sizes. Therefore, it's difficult to provide an exact measurement.
However, we can offer advice on sizes that generally work well on various screen sizes.
For width, we recommend maintaining a minimum width of 1920px. This ensures that your image will always appear sharp on all screens.
For height, we recommend maintaining a minimum height of 800px. You can use the bottom and top 100px as a safety margin. Make sure no elements that you always want to display in the header are present in this area.
In terms of positioning, it's crucial to have the most important elements in the photo as close to the center of the image as possible. This helps prevent them from being cut off on certain screen sizes.
Click here for more information on responsive design.