Referral & Household Invite Protocol

Technical contract governing how household invite codes are structured, validated, and passed through the Google Play Store installation funnel.

Standard 1

Crockford Base32 Code Grammar

Invite codes use Douglas Crockford's Base32 encoding to avoid visual ambiguity (e.g. confusing 1 with I or l, or 0 with O) and accidental offensive words:

Alphabet (32 symbols): 0123456789ABCDEFGHJKMNPQRSTVWXYZ

Length: 8 characters (Format: XXXX-XXXX or XXXXXXXX)

Validation Regex: /^[0-9A-HJKMNP-TV-Z]8$/i (after removing hyphens)

Standard 2

Google Play Referrer String Contract

When an invited user taps a referral link on mobile, the web router redirects to Google Play with a strict referrer parameter:

// Public Link Format:

https://getkestro.in/r/KEST-7428

// Transformed Google Play Destination:

https://play.google.com/store/apps/details?id=in.kestro.app&referrer=ref%3DKEST7428

Upon first app launch, the Flutter client uses Google Play Install Referrer to read ref=KEST7428 and pre-fill the join modal automatically.