The use of marijuana in Austria is not technically illegal. However, production and possession of cannabis is in fact illegal. You could face up to one year in prison for possession but Austria allows offenders to complete probation or drug rehabilitation instead. If you do neither of these then you will likely be subject to pay a fine to the courts.
Growing marijuana in Austria is not severely punished as long as you are not producing. The Austrian law recognizes producing as separating the buds from the plant. Large factories exist that sell marijuana clones legally, but once you take it into the flowering stage you are committing a crime. Large amounts over 200 grams is considered a serious crime and Austrian law enforcement will take into account any evidence they find at your grow. This can include old trimmings or other information pointing at an obvious past of production.
Generally they will not seek out smokers but you would be wise to keep it in private.
Where to buy marijuana in Austria
If you have no connections, go for a walk in the city park. Sit down and observe or walk around looking out for either black men on bicycles, groups of Albanians, Arabs or Austrian youngsters in hip-hop style clothing. Usually they will notice you and walk by asking “Brauchsch was?” meaning “Need some?” or “Haschd Was?” meaning “Got some?” Be careful of undercover police.