Learn Hardcore Finnish: Kun asioi verkossa, pitää noudattaa samoja sääntöjä. - When you handle things online, you have to follow the same rules.

Kun introduces a time clause (a subordinate clause) meaning when/whenever.
So Kun asioi verkossa is a general “whenever someone is dealing/doing errands online” type of clause, setting the situation for the main clause (pitää noudattaa…).

Where is the subject in Kun asioi verkossa? Who is asioi referring to?

There is no explicit subject because Finnish is using the zero person (nollapersoona): the 3rd person singular form (asioi) is used with a generic meaning like when you/one/people do X.
It’s deliberately nonspecific: it applies to anyone in that situation.

Could it also be Kun asioit verkossa (with -t)?

Yes. Kun asioit verkossa would directly address you (singular).
Kun asioi verkossa is more general/impersonal, like a rule or guideline that applies to everyone.

Is asioi a present tense form? Why present tense in a rule-like sentence?

Yes, asioi is present tense (3rd person singular) of asioida. Finnish often uses the present tense for general truths, instructions, and habitual situations—similar to English using present tense in rules.

What does pitää mean here, and why is there no subject with it either?

Here pitää + infinitive expresses obligation: must/should.
It’s used impersonally: pitää noudattaa… ≈ it is necessary to follow… / one must follow….
That impersonal style matches the zero person in the first clause.

How is pitää noudattaa constructed? What form is noudattaa?

After obligation-pitää, Finnish uses the 1st infinitive (dictionary form) of the main verb.
So noudattaa is the infinitive “to follow/comply with”, and pitää noudattaa means “must follow”.

Why is there a comma: Kun asioi verkossa, …?

In Finnish, a subordinate clause (here the kun-clause) is normally separated from the main clause with a comma.
So Kun asioi verkossa, pitää… follows standard punctuation rules.

Why is it samoja sääntöjä (partitive plural) instead of something like samot säännöt?

The object of noudattaa is typically in the partitive: you “follow rules” in general rather than pointing to a single fully-bounded set as a completed whole.
So noudattaa sääntöjä is the normal pattern, and samoja agrees with sääntöjä in case and number (partitive plural).

How do the forms samoja and sääntöjä break down?

sama → partitive plural samoja
sääntö → partitive plural sääntöjä (plural marker -j- appears in many plural partitives)
They match because adjectives agree with the nouns they modify in Finnish.

What case is verkossa, and why that case?

verkossa is in the inessive case (-ssa/-ssä), meaning in something.
So it literally means in the net/in the online environment, i.e. online.

Could the word order be changed?

Yes. For example: Pitää noudattaa samoja sääntöjä, kun asioi verkossa.
Both are grammatical. Putting the kun-clause first is common when you want to set the context first; putting it last can feel a bit more like adding a condition after the main point.

Are there alternatives to pitää here, and do they change the tone?

Common alternatives:

täytyy noudattaa = must (often feels a bit more direct/strong)
on noudatettava (passive necessive) = must be followed (more formal/written)
on pakko noudattaa = have to (strongest/most forceful)