Is there a completely free, open-source booking system I can self-host?

Cal.com is the closest — the core is MIT licensed and you can self-host it on your own infrastructure. It's strong for one-on-one professional scheduling. For service business booking (salons, fitness studios, equipment rentals with per-staff schedules and group sessions), the open-source options are thinner. Opencals offers MIT-licensed frontend templates, but the booking backend is a managed SaaS.

What is the difference between an open-source booking template and a self-hosted booking system?

A self-hosted booking system means you run the entire stack — the backend logic, the database, the availability engine. An open-source booking template is a frontend codebase (the website) that connects to a managed API backend. You own and can fully customise the code, but the backend infrastructure is managed by the API provider. Templates get you to production faster; self-hosting gives you full data sovereignty.

Can I use the Opencals templates for client work?

Yes. The templates are MIT licensed — you can use them for commercial client projects, rebrand them, fork them, or use them as the starting point for a custom design system. Each client gets their own Opencals account and API key. There's no per-site licensing fee on the template code.

Does Cal.com support multi-staff, multi-location service business booking?

Cal.com is primarily optimised for one-on-one professional scheduling (consultations, sales calls, interviews). Multi-staff team scheduling exists but is positioned as a team/enterprise feature. It's less suited to the service business pattern (salon with 6 stylists, 3 locations, group classes) than a dedicated service-commerce platform like Opencals.

Is the Opencals Storefront API itself open source?

The API backend is not open source. The frontend templates and the TypeScript SDK are MIT licensed. The API is a managed SaaS — Opencals runs the backend infrastructure, you call it via REST. If full backend open source is a hard requirement, Cal.com's self-hosted option is the better fit.

The Best Open-Source Booking Systems in 2026

"Open source" means different things depending on what you're searching for. A salon owner looking for free booking software has different needs than a developer wanting to self-host a scheduling backend, which is different again from an agency that wants to clone and rebrand a booking website for clients.

This guide covers the main open-source booking options in 2026, separated by what they actually are and who they're for.

There are three distinct categories: self-hosted booking platforms (you run the whole stack), open-source booking website templates (clone and deploy with a managed backend), and open-source SDKs and API clients (for developers building custom integrations). Match the tool to your actual need.

Category 1: Self-hosted booking platforms

These are complete open-source applications you install and run on your own server. You control everything — the code, the data, the infrastructure. The tradeoff is that you're also responsible for uptime, security updates, and database management.

Cal.com

Cal.com is the most prominent open-source scheduling platform. It started as an open-source alternative to Calendly and has grown into a full scheduling infrastructure product, with a hosted SaaS offering alongside the self-hosted option. The core is MIT licensed.

Best for: Developers who need one-on-one appointment scheduling for professional services (consulting, sales, interviews) and want to self-host or contribute to an active open-source project.

Pros

Very active community and contributor base
Clean, modern UI out of the box
Good integrations: Google Calendar, Zoom, Stripe, webhooks
Both self-hosted (MIT) and hosted SaaS options
Strong API for custom integrations

Cons

Optimised for one-on-one professional scheduling, not service business booking
Multi-staff and multi-location are enterprise features
Self-hosting requires Docker, a database, and ongoing maintenance
Group sessions, deposits, and rental-duration pricing are limited

Rallly

Rallly is a lightweight open-source scheduling poll tool — think Doodle, but self-hosted. It's not a booking system in the service-business sense; it's a tool for finding meeting times among a group of people.

Best for: Teams that need a self-hosted Doodle replacement. Not for customer-facing appointment booking.

Formbricks

Formbricks is an open-source survey and feedback platform, sometimes grouped with scheduling tools. It's not a booking system.

The self-hosting reality check

Running a self-hosted booking system means you own the infrastructure. Budget for a VPS, a managed database, SSL certificates, backup strategy, and time to apply security patches. For most service businesses, the math works out in favour of a managed SaaS product unless the data sovereignty or customisation need is strong.

Category 2: Open-source booking website templates

These are complete, production-ready booking website codebases — MIT licensed, publicly available on GitHub — that connect to a managed booking backend through an API. You get the benefits of open source (clone it, read the code, customise it, rebrand it) without running the backend infrastructure yourself.

This category has grown significantly with the rise of headless booking APIs. The backend stays managed; the frontend is yours.

Opencals open-source templates

Opencals publishes MIT-licensed Next.js booking website templates built on the Opencals Storefront API. The current available template:

Haar — a complete beauty salon booking website. Services, staff, multi-location booking, real-time availability, Stripe checkout, customer accounts. Next.js 15, TypeScript, Tailwind. One-click Vercel deploy.

Pros

Complete booking flow out of the box — nothing to wire up from scratch
MIT licensed — use it for client work, rebrand it, fork it
Managed backend — Opencals handles availability, payments, data; you own the frontend
One-click Vercel deploy — working booking site in minutes
Actively maintained and updated with the API

Cons

Backend is Opencals (managed SaaS) — the template code is free, the backend is paid
Currently one template (Haar/salon); more in development
Frontend-only open source — the API backend is not self-hostable

Deploy with Vercel

The Haar template is the reference implementation of the Storefront API — every API call is documented in context in the source code. Even if you don't use the template directly, it's the fastest way to understand how to build a production booking frontend on the Opencals API.

Category 3: Open-source SDKs and API clients

These are open-source libraries for integrating with booking backends, not complete applications.

@opencals/storefront-sdk

The official TypeScript SDK for the Opencals Storefront API. Generated from the OpenAPI spec — every request and response is fully typed. Ships with Zod schemas for runtime validation and formatting helpers.

bash

npm install @opencals/storefront-sdk

MIT licensed. Source on GitHub · npm · SDK guide

Choosing the right option

	Cal.com (self-hosted)	Opencals templates	Opencals SDK
Who operates the backend?	You	Opencals (managed)	You bring your own backend
Infrastructure responsibility	Full	None	Depends on backend
Frontend customisation	Limited to themes	Full (fork the template)	Build from scratch
Service business booking	Limited	Yes — salon, spa, fitness, rentals	Yes, via API
Multi-staff + multi-location	Enterprise tier	All plans	All plans
Group sessions	Limited	Yes	Yes
Open-source code	Entire platform (MIT)	Frontend template (MIT)	SDK (MIT)
Best for	Devs who want to self-host scheduling	Agencies / devs building client sites fast	Devs building fully custom integrations

The agency use case

Agencies building booking websites for multiple clients should pay attention to the templates approach. The pattern:

Clone the Haar template (or fork it into your own design system)
Each client gets their own Opencals account and Storefront API key
Deploy the same codebase with a different API key per client
Customise the theme, copy, and brand per client — the booking logic is unchanged

You write the integration once. Every subsequent client deployment is a theme and brand change, not a new development project. The backend pricing is per-booking or a low monthly plan, so client projects are easy to price.

Browse open-source templates

The full Opencals template gallery — current and upcoming.

Haar template documentation

Full details on the salon booking template — stack, features, setup.

What is a headless booking system?

Architecture overview for teams evaluating the API-first approach.

Opencals for developers

API, SDK, templates — everything for building custom booking experiences.

The best open-source booking systems in 2026 (and when to use each one)