Why does he go offline when I come online on WhatsApp

One disappearance means very little. What matters is whether the pattern holds across several days and whether his replies are warm when they come. Look at what he sends when he does reply. If his messages are engaged, he asks you things back, and he mentions specifics from your conversation, then the offline habit is probably just how he uses the app. If his replies are short, late, and carry no follow-up, he may be keeping you at arm's length.

Also notice the rhythm. Some people only open WhatsApp at set times, like lunch or before bed. If he's consistently offline when you're free, that's a scheduling mismatch more than avoidance. Compare how often he starts a conversation himself. Someone interested tends to initiate at least some of the time.

Aim to message in a way that doesn't depend on whether he's online. Send something that stands on its own, with a question or a point he can answer whenever he gets to it. Skip messages that only make sense if he replies right now, like asking if he's free this minute. A message that reads fine whether he sees it in five minutes or five hours takes the pressure off.

If you notice you keep timing your messages to his online window, step back. That tends to make the chat feel like a status check. Pick a rhythm that suits your own day, and let his replies arrive on his schedule.

Give it a reasonable window, maybe a few days to a week of normal back-and-forth, before you decide what the pattern means. If he's consistently offline, slow to reply, and never makes an effort to meet or plan, you can stop putting extra energy into a chat that isn't being returned. You don't need to confront him. Reply when he messages, and let the conversation match his level of effort.

If he does make plans, keeps things going when he's around, and seems pleased to hear from you, the offline habit is probably just a habit. Trust the overall pattern over any single moment you see him vanish.