Works well. There's an option to auto-refresh the page when you switch on or off.

Great extension! It helped me to be more concentrated while reading. If there is something to say about this app, sometimes the alternate texts on images pop out from the image region and overlap other texts. So it would be better if it shows a simple place holder instead (like what you see on in Android Firefox if you block 'Show images' in 'Settings' > 'Advanced'> 'Data saver' ).