Helene Groenberg

WhenPilot is a lightweight appointment booking plugin for small businesses — salons, clinics, consultants, tutors. Everything stays on your own site; there is no third-party booking service.
Features
<ul>
<li>Define services (name, duration, optional price, description).</li>
<li>Set your weekly opening hours in a simple text format (e.g. <code>Mo-Fr 09:00-17:00</code>).</li>
<li>Visitors book with the <code>[whenpilot]</code> shortcode: pick a service, a date, and a free time slot computed from your hours and existing bookings.</li>
<li>Double-booking prevention: slots are re-validated on the server before saving, with a configurable capacity (e.g. number of staff).</li>
<li>Admin inbox: see upcoming/pending/confirmed/cancelled bookings, confirm, cancel or delete.</li>
<li>Email confirmations to the customer and a notification to you, plus emails when you confirm or cancel.</li>
<li>Configurable lead time, how far ahead people can book, currency label and an optional auto-confirm.</li>
<li>Uses your site’s timezone. Works with any theme.</li>
</ul>
Usage: create a page, add the shortcode <code>[whenpilot]</code>, and publish.
All features described above are fully functional in this plugin — no time limits, no usage caps, no locked options. WhenPilot does not connect to any external service. A separately distributed companion plugin offers additional features (multiple staff/resources with custom fields, automatic email reminders) but is not required for the plugin to work.
<h3>Privacy</h3>
Bookings (name, email, optional phone and notes) are stored in your own database and emailed to you and the customer. No data is sent to any third party.

WhenPilot

Self-hosted appointment booking: services, weekly hours, free-slot picking, double-booking prevention and email confirmations.

igor800

Robina is a free, open-source booking and appointment plugin for WordPress, built for service businesses that want a capable booking system without subscription fees. It is service- and resource-centric: the bookable unit is a service with its own availability, while staff, locations and resources are optional layers you add only if you need them.
<h4>Highlights</h4>
<ul>
<li>Front-end booking widget (Vue 3). A clean multi-step wizard — Service, Date & time, Details, Confirm — added to any page with the <code>[robina_booking_form]</code> shortcode, or as a popup button with <code>[robina_booking_button]</code>.</li>
<li>Capacity-aware availability. Slots are computed from your business hours, slot step and buffers. Assign staff to a service and each one adds a parallel slot; a staff member booked anywhere counts as busy. With no staff, a service has a single capacity per location.</li>
<li>Group classes. Give a service a capacity above 1 (say 20 or 40 — there is no upper limit) and several customers can book the same session until it fills up — ideal for classes, workshops and large group sessions.</li>
<li>Staff (optional). Tag the people who provide a service, pin them to one or more locations, and give them their own weekly hours. When a customer picks a location, only the staff who work there are offered.</li>
<li>Locations (optional). Offices or branches with their own optional weekly hours; each service declares where it is available.</li>
<li>Native WordPress admin. A branded Catalog (services, categories, resources), a Month/Week/Day Calendar with in-place booking creation, plus Bookings, Customers, Staff and Locations screens — all in plain WordPress UI.</li>
<li>Email notifications to the owner and the customer on every new booking.</li>
<li>Optional online payments — Pay on site, WooCommerce, Stripe or PayPal (see “External services” below). Leave them all off for free bookings.</li>
<li>Self-contained and private. No external CDNs and no trackers; the phone-input flags and every front-end asset ship inside the plugin. Uninstalling removes Robina’s tables and options.</li>
</ul>
<h4>Service-centric by design</h4>
Robina deliberately keeps availability on the service, not on a mandatory “employee”. Staff, locations and resources are optional capacity and scope layers, so Robina also suits non-staff models such as equipment rental or table booking.
<h3>External services</h3>
By default Robina works entirely on your own site and contacts no third party. It only talks to an external service when you, the admin, enable and configure a payment gateway, and only when a customer actually chooses to pay with it. No data is sent anywhere otherwise — Robina has no “home” server and sends no telemetry or analytics.
Stripe — used only when you enable “Stripe” and enter your API keys. When a customer pays by card, Robina creates a Stripe Checkout Session and redirects the customer to Stripe’s hosted payment page, and it receives Stripe webhooks to confirm payment. Data sent to Stripe: the booking amount, currency, a short description and the customer’s email. Card details are entered on Stripe’s site, never on yours. 
Terms: https://stripe.com/legal — Privacy: https://stripe.com/privacy
PayPal — used only when you enable “PayPal” and enter your client ID and secret. When a customer pays with PayPal, Robina creates a PayPal order, redirects the customer to PayPal to approve it, then captures it on return. Data sent to PayPal: the booking amount, currency and a reference id. 
Terms: https://www.paypal.com/legalhub/home — Privacy: https://www.paypal.com/legalhub/privacy-full
WooCommerce (optional, local) — if you enable WooCommerce checkout and WooCommerce is installed, Robina creates a pending WooCommerce order and hands payment off to WooCommerce. Robina makes no external call itself; any outbound requests are made by WooCommerce and its own gateways under their policies.
Map link — a location’s address is turned into a plain “view on map” link to Google Maps (https://www.google.com/maps/search/…). It is only a link: nothing is transmitted and no map is loaded unless a visitor clicks it.
<h3>Source code</h3>
Robina is fully open source (GPLv2+). The front-end widget is compiled with Vite from the Vue source that ships inside the plugin under <code>/resources</code>. The build files (<code>package.json</code>, <code>package-lock.json</code>, <code>vite.config.js</code>) are bundled too, so the compiled assets in <code>/assets/dist</code> can be regenerated from source with:
<pre><code>npm install && npm run build
</code></pre>
Bundled third-party libraries (installed via npm, both MIT-licensed):
<ul>
<li>Vue 3 (^3.4) — https://github.com/vuejs/core</li>
<li>intl-tel-input (^29.0) — https://github.com/jackocnr/intl-tel-input</li>
</ul>

Robina

Free, open-source booking and appointments for WordPress: services, staff, locations, capacity-aware availability and optional payments.

WhenPilot vs Robina