The interface is basic as all it needs to support is a limited number of options.
Moreover, CodecViewer detects the codecs which are already installed to your computer.
On the other hand, it can’t manage the codecs it finds on your system and it won’t provide you with direct download links for the missing codecs.
CodecViewer is an item you would want to keep on your computer just in case you can’t play an AVI file.
Showing the codec you need to play your AVI files is the only task this application can do, so its size is very small and its system resource requirements, minimal.