In a fast market, an enthusiastic yes over WhatsApp often lands before anyone has read the contract properly. Whether that message already binds a tenant, and what phrasing keeps the door open, matters to anyone juggling two promising viewings in the same week.
Legally, yes, in most cases — but the nuance around verbal agreements is real and worth taking seriously. Residential tenancies require written form, and courts tend to be cautious about binding a consumer tenant to something unsigned. That said, Dutch case law has held that a clear verbal or WhatsApp exchange covering the essentials — rent, address, move-in date, mutual "yes" — can already form a binding oral agreement, especially if the landlord relied on it by taking the listing down or turning other applicants away. Practically: don't say "deal" until you mean it, and if you need to hold your spot while you think, say explicitly you're agreeing "subject to signing" (onder voorbehoud van ondertekening). If you haven't paid anything and nothing's been put in writing as final, walking away is usually low-risk.