Another point about 9 line slot machines that should. They are the machines that feature the old school games with an armed bandit.
Up until late 2002 you could not find any online slots with nine lines. This changes when Microgaming released Treasure Nile, 5 Reel Drive and Reel Thunder and Playtech released Highway Kings and Captains Treasure.
Even so it's pretty clear that the 5 reel, 9 line slot machines are favorites for a lot of players.
For this reason you should always check the pay table before you start playing so you know where the lines are. In some cases there are even different line layouts from the same software players providers.
These games were an instant hit with players and have seen the nine line slot range grow ever since. There are several different nine line layouts with Microgaming, Playtech and Cryptologic all using different line layouts.
The popularity of the nine line format has probably already peaked with new releases online and offline slowing down over the last few years.