Here are the best open‑source appointment scheduling tools I’d actually recommend for a small business, based on real-world use, features, and how actively they’re maintained.

⭐ Best overall: Cal.com

• Open-source (MIT license), very actively developed
• Self-host or use their hosted version
• Features: booking pages, team scheduling, calendar sync (Google/Microsoft), Zoom/Meet integrations, payments, workflows
• Very close to Calendly in UX

Why it stands out: it’s basically the de facto open-source Calendly alternative, with full feature parity and strong customization (stackfyi.com)

Good fit:

• Consultants, agencies, service businesses
• Anyone who wants modern UX + flexibility

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For teams that specifically want self-hosted scheduling rather than a SaaS like Calendly, the strongest modern option is Cal.com / Cal.diy, with a few other open‑source tools (Easy!Appointments, Booked Scheduler, Koalendar, Zcal) worth considering depending on how technical your team is.

Below are the options you should look at first, broken down by team‑fit and self‑hosting support.

1. Cal.com / Cal.diy – Best full‑featured, team‑ready self‑hosted alternative

When to choose it: Tech‑savvy teams that want a real Calendly replacement with team scheduling, round‑robin, deep integrations and full control over infrastructure.

• Self‑hosting & open source
• Cal.com has long been the default…

You can let clients book meetings automatically by using an online scheduling tool (like Calendly, Cal.com, or Square Appointments), connecting it to your calendar, and sharing a booking link where people pick a time without emailing you first.

Here’s a simple, practical setup:

1. Pick a scheduling tool (quick recommendations)

All of these let clients see your availability and book directly, with automatic confirmations and reminders.

• Calendly – very popular, easy to use, great for 1:1 calls and simple team scheduling.
• Cal.com – more customizable and developer-friendly, strong automations.
• Square Appointments – good if you offer services and might want to take payments or run a s…

Here are a few solid scheduling tools that sync with Google Calendar + send automatic reminders, depending on how simple or advanced you want:

✅ Easiest / most popular: Calendly

• Syncs directly with Google Calendar (real-time availability)
• Lets people book via a link
• Sends automatic email + SMS reminders
• Clean, dead-simple setup

Why it’s good: it’s basically the default for scheduling links, and it handles reminders + follow-ups well out of the box (acuityscheduling.com)

👉 Best for: 1:1 meetings, freelancers, client calls

✅ More customizable (great for businesses): Acuity Scheduling

• Google Calendar sync
• Automated email + SMS reminders
• Lets you take payments, sell packages,…

For one-on-one meetings with integrated video conferencing, the strongest Doodle alternatives are Calendly, SimplyMeet.me, YouCanBookMe, Acuity Scheduling, Zencal, Cal.com, and all‑in‑one tools like MeetFox or SchedulingKit.

Below are the options most worth considering, focusing on 1:1 scheduling plus Zoom/Meet/Teams-style integration:

1. Calendly – widely adopted, strong video integrations

Best for: Individuals, teams, and enterprises who want a polished, standard booking experience.

• Designed for one-on-one and team scheduling, not polling.
• Integrations: Zoom, Google Meet, Microsoft Teams and many others.
• Creates a unique video meeting link for each booking via these integration…