Hanoi's violent crime rate is lower than any European capital — I walk home at 1am regularly. The real dangers, in order: 1) crossing the road (2 million motorbikes, right-of-way is theoretical — walk slowly and predictably, never stop mid-stream), 2) motorbike taxi accidents (insist on the helmet, decline if the driver seems drunk), 3) food poisoning from ice in cheap juice stalls. Zero of these end most trips, but each ends some.
1) The Ta Hien beer swap — friendly local invites you upstairs, $200 bill arrives. Only drink where prices are chalked up. 2) The shoeshine grab-and-repair — a man grabs your shoe, "fixes" it, demands $20. Say no firmly and walk on. 3) Fake taxis at the airport — only use Grab, or the official Vinasun/Mai Linh queue. A genuine airport-to-Old-Quarter fare is $10-14; anything over $25 is a scam.
Hanoi is one of the easier Asian capitals for solo female travel — harassment is rare, dress codes are relaxed, and dormitory hostels in Hoan Kiem are well-run. Common-sense stuff still applies: don’t leave a phone on a cafe table facing the street (drive-by grabs happen on Ta Hien), and use Grab after midnight rather than walking through the unlit stretches near Long Bien bridge.
Curated picks are coming — meanwhile, the live search covers every bookable property at the same price or better.