Same relationship, same outcome — permanent residency — but two very different journeys to get there. Whether you apply for an onshore or offshore partner visa in Australia comes down to one simple fact: where you physically are when you lodge. That single detail changes your bridging visa rights, your travel options, and even how urgently you need to act.
In short: Onshore applicants (Subclass 820 → 801) must be in Australia when they apply, and are automatically granted a Bridging Visa A, letting them stay and generally continue working while the application is processed. Offshore applicants (Subclass 309 → 100) apply from outside Australia and receive no bridging visa, since they're not in the country while the case is decided.
Onshore: Subclass 820 → 801
You can lodge a Subclass 820 application while lawfully in Australia on almost any substantive visa — student (500), visitor (600), temporary work (482), graduate (485), and others. Your current visa type doesn't determine eligibility; being lawfully present at lodgement does.
The biggest practical advantage is the Bridging Visa A, granted automatically once your 820 is lodged. It activates when your current visa expires and lets you remain in Australia lawfully — often with work rights — while your case is assessed. If you need to leave the country during this period, you'll need a Bridging Visa B first.
Offshore: Subclass 309 → 100
The 309 must be lodged while you're outside Australia, and generally you need to still be offshore when the temporary visa is granted. There's no bridging visa here, since you're not onshore to need one — but you can still visit Australia on a separate visa (like a Visitor visa) while your application is pending, subject to that visa's own conditions.