As of Houdini 20.5, use Copernicus nodes instead of Compositing nodes. Though both networks still exist, the Compositing network is now designated as COP Network - Old.

Though there are some similarities between the Copernicus and Compositing networks, this page explains key differences between the two.

Data and display windows both provide coordinates for a rectangle.

The data window determines which region (in pixel space) of the viewer contains pixel data. The display window determines the file’s boundaries (in pixel space) based on pixel coordinates in the upper-left and lower-right corners. For files that either don’t have all pixel data in the display window or have pixel data outside of the display window’s boundaries, the extra pixel data appears between the data and display windows.

(Thanks to OpenEXR and fnord software blog for reference.)

The Compositing network has the Limit node, which lets you limit the pixel range. Use the Clamp node to perform a similar function in Copernicus.

Use the Contact Sheet COP in Copernicus to perform a similar function as the Mosaic COP2 node. To offset file sequences, update $F# ($F4 for example) in the File COP's File Name to <F#> (<F4>). This lets you set the Video Start Frame to the frame number from where you want the sequence to start playing. $F# doesn’t use the Video Start Frame.

Turn on Extract Tile in the Crop COP to perform a similar function as the Labs Demosaic COP2 node.

The Compositing network could support multiple layers on one wire. Instead, each Copernicus wire supports only one layer.