May someone add me to a WhatsApp group without asking?

Short version: adding your number to a group where other members see your number is technically "processing personal data" — a phone number is personal data. But this falls under the "household exception" (GDPR Art. 2(2)(c)) if purely private: family, friends, classmates. GDPR doesn't apply. When DOES GDPR apply? When the group has a professional, organisational or commercial purpose — e.g. employer adds you to a work group, sports club board adds members, school app for parents. Then a legal basis is needed (consent, legitimate interest, etc.) + you must be informed. What can you do? Leave the group immediately (group info → "Leave group"). Ask the admin to remove your number from their phone book / contacts. On persistent spamming: block the admin. For commercial abuse: e.g. a seller adds you to a "Marktplaats selling" group — that's direct marketing without consent. Forbidden under GDPR Art. 21 + Dutch Telecom Act Art. 11.7. Tell the admin "stop now, no consent" + on refusal complain to ACM or AP. For group admins: always ask first. Be clear about purpose, who reads along, how to leave. Best practice: send a private message "May I add you to group X for purpose Y?" first — avoids complaints and friction. Special settings: in WhatsApp you can set who may add you (Settings → Privacy → Groups → "My contacts except…" or "Nobody").