Event properties

Properties enrich an event with structured data. They let you filter, group and analyse without multiplying event names.

#Format

window.wmf('event', 'purchase', {
  plan: 'pro',
  value: 49,
  currency: 'EUR',
  trial_days: 30,
});

#Strict server-side rules

• Up to 10 keys per event. The 11th and beyond are silently dropped.
• Key: 50 chars max, [a-z0-9_]+ (lowercase + digits + underscore).
• Value: string, number or boolean. Objects, arrays and null are rejected.
• String: 200 chars max. Anything longer is truncated.
• No PII: no email, no name, no phone number, no token. This is enforced by our CNIL commitment — see Compliance.

#Best practices

• Use value (number) for amounts: it gets aggregated automatically (sum + average).
• currency (ISO 4217 3-letter string): if present, it's displayed next to value.
• Use short enum values (plan: 'pro' rather than plan: 'Pro plan with unlimited access').
• Don't duplicate context: if you pass page_url, know that we already store it at event level.

#Why these limits?

Raw events live 90 days in a jsonb table with a GIN index. The limits guarantee:

1. A bounded payload size (16 KB at the server).
2. A reasonable cardinality (or aggregates become unmanageable).
3. GDPR compliance (the payload can't be repurposed for fingerprinting).