A safe-haven currency is one that investors tend to buy during periods of market stress, geopolitical uncertainty, or risk aversion, because it's seen as more stable or liquid than riskier alternatives — the US dollar, Japanese yen, and Swiss franc are the classic examples. Demand for safe havens typically rises sharply during equity sell-offs or global crises.
The flip side is "risk-on" currencies (like AUD or NZD), which tend to strengthen when investor sentiment is calm and appetite for riskier assets returns.
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Guide
How to Check the Way a Currency Is Managed
The regime behind a currency is published, not inferred. The four primary sources that say how a rate is governed, what each one can and cannot tell you, and how to keep the answer from going stale.