Cal.com

Google Calendar is a time-management and scheduling calendar service developed by Google. It provides web and mobile applications for creating and sharing events, reminders, and multiple calendars, and integrates with Gmail and Google Workspace.

SnagTime is a free, self-hostable scheduling application that provides account and workspace management, event types, availability rules, public booking links, time-zone handling, custom booking questions, rescheduling, cancellation, and recovery links. It checks Google Calendar free/busy status and can create calendar events, sends organizer and invitee messages through SMTP, and supports Stripe Checkout in test mode with webhook confirmation and refund handling. The local demo uses SQLite, a local calendar adapter, a local email inbox, and stub payments; production deployments use a PostgreSQL architecture with a web service, background worker, persistent database, and webhook endpoints. The application is a Next.js project with Prisma schemas and migrations, distributed under the MIT License. It is intended for self-hosting rather than as a managed service; external Google Calendar, SMTP, Stripe, hosting, domain, and database services must be supplied and configured by the operator.

GoHighLevel (HighLevel) is an all-in-one sales and marketing platform for digital agencies. It provides CRM, marketing automation, landing pages, and white-labeling capabilities that agencies can resell to their clients.