Bitcoin bulls have one price level to defend

"The level to watch is $82k," said Jeff Anderson, head of U.S. at crypto trading firm STS Digital. He pointed to the double top at that level, a chart pattern shaped like the letter M that forms when prices hit the same peak twice and fail both times.

"A breakdown will probably yield a slip back into the high 70s," Anderson said.

He doesn't see a drop as the end of the rally, though. U.S. inflation and shaky confidence in U.S. government debt are the kind of forces that tend to help bitcoin over time. "Any move like this would be well supported," he said.

Anderson blames the recent weakness on the bond market rather than on bitcoin itself. U.S. Treasury note prices are falling and yields are climbing. When yields on safe government bonds rise, riskier assets like crypto can look less attractive.

"Current softness this week is a direct result of yield markets unravelling and volatility exploding in fixed income space," Anderson said. "At the current pace it feels like treasuries will keep selling off until equities finally crack out!"

Lacie Zhang, a research analyst at Bitget Wallet, sees the $81,500 to $83,000 zone as the key area.