How can I tell if someone blocked me on WhatsApp? My messages aren't going through.

WhatsApp never tells you outright, so you're reading signs, and no single one is proof. The strong signs, especially together: one grey tick that never becomes two (sent but never delivered), their profile photo disappears or freezes on an old one, you can't see their last seen or online status, and calls to them don't connect. Any one alone can be innocent (they're offline, changed privacy, lost their phone). All of them at once, for a while, usually means blocked.

One grey tick that never becomes two is the biggest tell, but alone it just means undelivered, they could be out of signal for days. Look for the combo: no photo, no last seen, calls failing, all together.

A sneaky check: try adding them to a group. If you're blocked, WhatsApp usually won't let you and shows an error. Not definitive, but another data point.

Honestly, if someone blocked you, the kind move is to leave it. The signs are deliberately vague because WhatsApp doesn't want to fuel exactly this anxiety.