Some reactions to real-world situations only make sense if you've spent way too much time in internet spaces. Chronically online describes exactly that disconnect, calling out a perspective shaped a little too heavily by internet-specific culture.
What this phrase actually describes
This phrase describes someone whose views, references, or reactions are shaped heavily by internet-specific culture, to the point that their perspective feels noticeably disconnected from how most people outside those online spaces would actually think or talk about the same situation.
More than just spending time online
This phrase targets a skewed perspective specifically, not simply the amount of time someone spends online — someone can use the internet constantly without being described this way, as long as their views stay grounded outside of internet-specific logic.
How this phrase gets used
This phrase is most often used critically, gently mocking someone for reacting to an ordinary real-life situation using distinctly internet-native logic, slang, or outrage that wouldn't make sense to someone unfamiliar with those specific online spaces. 
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Recognizing a chronically online reaction
A reaction often gets labeled this way when it applies niche internet slang, meme logic, or online-specific framing to a situation that most people outside those particular internet spaces wouldn't interpret the same way at all.
A lighthearted, self-aware use too
Beyond criticism of others, this phrase also gets used as a self-aware, lighthearted admission — someone jokingly acknowledging that their own reaction only makes sense because of how much internet culture has shaped their perspective.
Related to other internet-culture criticism
This phrase sits alongside other similar internet-culture criticisms, similar to how what does touch grass mean as an insult targets a related but distinct concern about being too immersed in online spaces.
Conclusion
Chronically online captures a specific, recognizable disconnect between internet-native logic and everyday real-world perspective. For more slang and internet culture phrases explained clearly, browse SoundGIFs' full News section.