If you take appointments — a salon, a clinic, a studio, a consultancy — booking software is the one tool you touch every day. The hosted names (Calendly, Acuity, Square Appointments) all meter you monthly, and they do not meter the same thing: Calendly counts seats — $10 each per month billed annually — while Acuity counts calendars, $16 a month billed annually for one and $49 for up to thirty-six (both read 5 September 2026). Square Appointments would not render its plan prices to us on that date, so it is named here without a figure rather than with a borrowed one. Here is the honest self-hosted field, including the free options, because a guide that hides them is an ad.
The open-source options (genuinely good — start here if you want free)
- Cal.com — the heavyweight, describing itself as "A fully customizable scheduling software for individuals, businesses taking calls and developers building scheduling platforms", with self-hosting still offered (read 5 September 2026). Open-source scheduling with a polished UI, team routing, and a huge integration surface. The trade-off: it is a modern JavaScript stack — self-hosting it means running a Node/Postgres deployment and keeping up with a fast-moving project. If you have the ops comfort, it is excellent.
One caveat this page owes you, since it is recommending Cal.com as the free option: that is true of the source, not of the service. Cal.com's own hosted plans are per-seat and not cheaper than the incumbent — Teams at $12 per user per month, Organizations at $28, billed yearly, above a free tier (re-read 11 October 2026). Signing up at cal.com is not the free route; running it yourself is.
- Easy!Appointments — the classic open-source PHP scheduler, which calls itself "100% free and Open Source" with "No monthly fees", usable "even for commercial use", on Apache or Nginx with PHP and MySQL (read 5 September 2026). Covers services, providers and working plans, and has been around for years. The trade-off: the interface and feature pace show its age, and deposits/payment-adjacent workflows are not its focus. (Optional paid Premium Services — custom development, managed hosting, white labeling, migration, support — sit beside the free software; none is needed to run it.)
If either of those fits your needs and your ops appetite, use it — free and self-hosted beats paid and self-hosted when the feature set covers you.
Where a paid, owned tool fits
Slotly is our commercial entry: a one-time purchase ($99, full PHP source) built around one obsession — a scheduling engine that cannot double-book, proven by its shipped test suite, plus deposits, reminders, and a clean admin on the same boring shared-hosting PHP stack as Easy!Appointments. You would pick it over the free options for the conflict-engine guarantee, the deposits workflow, and a maintained codebase you own outright without tracking an upstream project. Live demo — no signup. Since the 3.0 release it also carries a REST API and an MCP endpoint behind a scoped key; the direct answer to "self-hosted booking, simple to use, with an API" is the long form, and top booking software self-hosted options is the short one.
Try the Slotly demo ↗Live, on sample data, no sign-up.
The honest chooser
- Want free + full-featured and can run Node: Cal.com.
- Want free on cheap PHP hosting, simple needs: Easy!Appointments.
- Want conflict-proof booking with deposits, bought once, on the same cheap hosting: Slotly — or the Studio Suite if waivers, memberships and the door sign-in come with it.
- Want zero ops at all: stay on a hosted tool and accept the meter — that is the honest trade.
Whichever you pick, self-hosting means the client list lives in your database, not a vendor's. That is the point of the whole category.
Every vendor figure in this category also lives in the Price Observatory — verified, dated, and source-linked, free to cite — and the calculator turns those figures into your own three-year number in ten seconds. Slotly can also be hosted for you on Ownware Cloud — the honest trade-off guide covers when that's worth it.