Open source scheduling and booking tools

Booking pages, appointment systems and group polls

Scheduling software does two different jobs, and few tools do both well.

• Booking pages publish one host’s free time. The host connects calendars, defines meeting types and availability rules, and shares a link; a guest picks a slot and the meeting lands in the host’s calendar with a video link and confirmation emails. This is the Calendly model. Cal.diy, Tymeslot, Thunderbird Appointment and CloudMeet work this way.
• Appointment systems are a business variant of the same idea: customers choose a service and a staff member, and the back office manages providers, working plans and customer records. Easy!Appointments is built for salons, clinics and consultancies rather than for one person’s meeting link.
• Group polls collect availability from many people. In a Doodle-style poll the organizer proposes a few dates and participants vote on each; in a When2meet-style grid participants paint their free hours across a week. Rallly and Nextcloud Polls use the first approach, Timeful the second.

What happened to Cal.com

Cal.com was for years the best-known open source Calendly alternative, licensed under AGPL-3.0 with a commercially licensed enterprise directory. On 15 April 2026 the company announced that its production codebase had moved to a private repository. The public code continues as Cal.diy, now entirely under the MIT license, and the old calcom/cal.com address on GitHub redirects to calcom/cal.diy. Cal.diy keeps the scheduling engine, calendar and video integrations, but drops teams and organizations, round-robin, routing forms, workflows, SSO and insights, and its README recommends it for personal, non-production use. Cal.com itself is now a closed-source hosted product, so it is not listed here.

The practical consequence is that no open source tool in this list offers the full team feature set of Calendly’s business plans. Round-robin distribution and routing forms are the features most often missing.

What to check before you choose

1. The job. A single host’s booking link, a business with services and staff, or a poll for a group. Mixing these up is the most common mistake.
2. Calendars. Google and Microsoft 365 connections need OAuth apps that you register with each provider when you self-host. CalDAV support matters if your calendar lives on a self-hosted or standards-based server; Tymeslot, Thunderbird Appointment, Cal.diy and Easy!Appointments support it, CloudMeet does not.
3. Video links. Which providers can create a meeting automatically per booking, and whether a fixed link is the only option.
4. Booking rules. Buffers, minimum notice, booking windows, custom questions, approval of requests and group or seated events.
5. Self-hosting effort. Compare a single container with an embedded database (Tymeslot) with a Next.js monorepo (Cal.diy), a stack with Redis and Celery workers (Thunderbird Appointment), or a serverless deployment tied to Cloudflare (CloudMeet). Every booking tool needs working outbound email, or confirmations never arrive.
6. Licensing model. Rallly’s code is AGPL-3.0, but multi-user self-hosted instances are asked to buy a license key on an honor system. Tymeslot moved from a source-available license to AGPL-3.0 only in June 2026. Each app page explains these details.
7. Moving from the proprietary tool. Timeful can import When2meet events, but we found no documented importer from Calendly or Doodle in the other tools, so expect to recreate event types and open polls by hand.

Standards and personal data

Booking tools rely on open calendar standards. iCalendar (RFC 5545) defines the .ics format attached to confirmation emails, and iTIP (RFC 5546) defines how invitations, replies and cancellations are exchanged between calendar systems. CalDAV (RFC 4791) is the protocol for reading and writing calendars on a server, with scheduling extensions in RFC 6638; tools that speak CalDAV can work with self-hosted calendar servers instead of only Google and Microsoft.

Scheduling tools also store personal data about people outside your organization: invitees’ names, email addresses and answers to booking questions, and poll participants’ names and availability. Under Article 28(3) of the GDPR, a hosted service that processes this data for you acts as a processor and needs a contract with you. Self-hosting keeps the data on your own infrastructure, but its security, backups and retention then become your responsibility.

Projects not listed

Some projects in this area are not included. Cal.com is now closed source, as described above. LibreBooking is open source and active, but it reserves rooms and equipment rather than scheduling meetings. Crab Fit and Dudle have had no commits in more than a year. Framadate, Framasoft’s poll tool, is developed on Framasoft’s own GitLab and its GitHub mirror is archived, so it falls outside this directory, which reads project data from GitHub.