If someone came up with a “system” for counting cards online (doubtful) and can prove it works, then everyone would probably learn it and then try and put it into practice at a number of online casinos.
At present there is not a “proven system” for counting cards effectively. If one slot is invented then look out for a warning when you log on to your favourite casino along the lines of: “Card counters will be denied the privilege of playing at XYZ casino”.
Even if you can’t count cards to victory online, there are still some beatable casino games on the internet. To profit from them you need a good money management system, discipline to leave the game and come back when the conditions are more favourable and most importantly of all, patience.
Follow these three suggestions and you may end up better than if you ruin your otherwise relaxing game worrying over the penetration, i.e. how many cards are dealt out of the same shoe, throughout your gaming session.
If you must practice your online card counting techniques, only invest your money in safe, regulated casinos. If you are going to gamble online, you need to know that someone is looking out for your best interests as a player.