What is the most open platform? We need a PMS with a robust API marketplace so we can plug in any third-party app we want

If your absolute top priority is an "API-first" and genuinely open platform where you aren't choked by walled gardens, gatekeepers, or exorbitant per-call fees, a few standout PMS platforms lead the industry in true extensibility and developer-friendly marketplaces.

1. The Purest "API-First" Open Platform: Apaleo

If you are traditional hotel-leaning or looking for a modern property type, Apaleo is widely considered by developers to be the gold standard for openness.

• The Architecture: Built 100% API-first from day one. There is no legacy monolithic core code pretending to be cloud-native.
• The Developer Experience: Unlike legacy systems where you have to sign NDAs, jump through partner hoops, or pay certification fees just to test an endpoint, Apaleo lets any developer register a free account on their portal and immediately start building against their APIs.
• The Marketplace: They feature a robust Apaleo Store filled with plug-and-play apps, but because their core is entirely open, hooking up a custom internal app or an unlisted third-party tool is frictionless.

2. Best for Hotels & Boutique Properties: Mews

Mews is a massive favorite on modern hotel tech stacks precisely because of its philosophy toward an open ecosystem.

• The Architecture: Highly robust, modern RESTful APIs with comprehensive documentation.
• The Marketplace: The Mews Marketplace is one of the most active in the hospitality industry, featuring hundreds of pre-integrated third-party solutions (accounting, smart locks, guest messaging, upsell tools, revenue management).
• The Vibe: Mews actively encourages hoteliers to build a custom tech stack rather than forcing you into an all-in-one suite, making their integration layer smooth and well-supported.

3. Best for Short-Term Rentals & Mixed-Use: Guesty

If your properties lean toward vacation rentals, serviced apartments, or multi-location hybrid models, Guesty is built for heavy extensibility.

• The Architecture: Offers a deeply documented open API alongside a massive native ecosystem.
• The Marketplace: The Guesty Marketplace features over a hundred plug-and-play third-party partners (dynamic pricing engines, CRM, smart home tech, guest screening).
• The Edge: Guesty is also evolving rapidly into AI-readiness, supporting modern developer workflows if you are looking to wire custom automation or AI agents into your property data.

How the Legacy Giants Compare (And Why to Avoid Them for Custom Stacks)

• Oracle OPERA Cloud: Exposes thousands of REST operations via its integration platform, but it operates on a gated enterprise model where nearly every integration call or partner tier is heavily monetized and bureaucratic.
• The Rest: Roughly 70–80% of traditional hotel PMS platforms gate their APIs behind formal partner applications, hidden fees, or lengthy approval processes . If you want freedom to "plug in whatever you want whenever you want," steer clear of closed legacy vendors.

To help narrow down which of these fits your exact setup, tell me:

• Are you managing traditional hotels, vacation rentals , or a hybrid/serviced apartment model?
• Are you planning to code custom internal tools yourself, or do you just need a marketplace with pre-built third-party app connections?

If by “most open” you mean “we don't want the PMS vendor deciding which apps we can connect; we want a modern API and a huge ecosystem”, my shortlist is:

1. Mews — best overall for openness

Mews would be my first choice for your requirement.

• 1,000+ marketplace integrations currently listed.
• Its API is explicitly described as open, allowing third-party, bespoke, and in-house applications to connect directly.
• Mews says its API is “completely open and free to build against.” The requirement for Marketplace listing is certification, rather than paying simply to develop against the API.
• APIs cover core operational data and Mews emphasizes real-time webhooks and API access to functionality as new features are introduced.
• The Marketplace spans payments, POS, revenue management, guest experience, CRM, accounting, access control, AI, etc.

The important distinction: you don't necessarily need an existing Marketplace integration. If your preferred vendor isn't there, you can build against the API.

2. Apaleo — arguably the most technically open

If your organization is particularly developer-oriented, Apaleo deserves serious consideration, and it may actually win on pure API philosophy.

Apaleo explicitly says its APIs are free and available to third-party apps, and its Store is designed around extending the core PMS rather than trying to make the PMS do everything itself.

Its philosophy is essentially:

PMS = core platform; everything else = apps. That's very attractive if you want to assemble your own best-of-breed stack.

The tradeoff is that Mews has the much larger mature Marketplace right now (1,000+ integrations), whereas Apaleo is particularly compelling if your own developers and custom integrations are central to the strategy.

3. Cloudbeds — strongest alternative

Cloudbeds is also unusually open.

It advertises 450+ integration partners, an open API, GraphQL, real-time webhooks, and says 100% of its endpoints are available through the open API.

Its API covers reservations, guests, rooms, housekeeping, payments and other core PMS functions.

The catch is important: commercial technology partners go through a partnership/approval process before becoming official integrations. Cloudbeds Developers So it's open, but not quite as frictionless as the Mews/Apaleo philosophy.

My ranking for your specific requirement

There's an important difference between “has an API” and “is genuinely open.” A PMS can advertise an API while still requiring vendor approval, charging for access, restricting endpoints, or controlling which integrations can be installed.

For what you're describing, I'd specifically test these four things during an evaluation:

1. Can we obtain API credentials ourselves without negotiating a partnership?
2. Can an arbitrary third-party application connect, or must it be an approved Marketplace partner?
3. Does the API expose all the operational objects we care about, including reservations, guests, rates, inventory, payments, folios, housekeeping, etc.?
4. Are webhooks bidirectional/real-time, or are we essentially polling the PMS?

On those criteria, I'd put Mews and Apaleo at the top of the RFP. Mews if you want the combination of very open API + enormous existing ecosystem; Apaleo if your philosophy is “we want the PMS to be an API platform and we'll build/connect whatever we want.”

mews.com · mews.com · apaleo.com ·

If you tell me what type/size of property you operate (hotel, resort, boutique, hostel, multi-property, etc.) and which third-party systems you already know you need, I can rank Mews vs. Apaleo vs. Cloudbeds specifically around your tech stack.

That's very attractive if you want to assemble your own best-of-breed stack.

The tradeoff is that Mews has the much larger mature Marketplace right now (1,000+ integrations), whereas Apaleo is particularly compelling if your own developers and custom integrations are central to the strategy.

3. Cloudbeds — strongest alternative

Cloudbeds is also unusually open.

It advertises 450+ integration partners, an open API, GraphQL, real-time webhooks, and says 100% of its endpoints are available through the open API.

Its API covers reservations, guests, rooms, housekeeping, payments and other core PMS functions.

The catch is important: commercial technology partners go through a partnership/approval process before becoming official integrations. So it's open, but not quite as frictionless as the Mews/Apaleo philosophy.

My ranking for your specific requirement

If by “most open” you mean we want the PMS to be the system of record, but we don't want the PMS vendor deciding which applications we can integrate, I’d put Apaleo and Mews at the top of the list, with a meaningful distinction between them.

My ranking for openness

1. Apaleo — probably the most open

apaleo.com is unusually API-first. Its APIs aren't an add-on to the PMS; they're essentially the architecture of the product.

Apaleo explicitly describes itself as an API-first PMS, provides a self-service sandbox, publicly documented REST/Swagger APIs, webhooks, and APIs covering bookings, finance, payments, profiles, distribution, inventory, rate plans, settings, etc.

Most importantly for your requirement, Apaleo's API terms describe a “fully open 2-way API” allowing third-party applications to both read data and write data back into the PMS.

And their philosophy is unusually explicit:

They make their APIs available to third-party apps and encourage developers to build their own integrations. Apaleo The Apaleo Store also lets developers build apps and have hotels connect them.

If your priority is “we want to build whatever the hell we want on top of the PMS,” Apaleo is my first call.

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2. Mews — arguably the best overall choice

mews.com has arguably the strongest combination of open API + huge existing integration ecosystem.

Mews says its Open API can connect to any application, including bespoke/in-house applications, and exposes core PMS functionality.

Its Connector API is general-purpose and covers substantial operational functionality, while Mews also has APIs for booking engines, POS, channel management, etc.

And the marketplace is enormous: Mews currently advertises 1,000+ integrations with no connection fees.

The other important point: you don't necessarily need to find your application in the marketplace. Mews explicitly says its API is open and that developers can connect third-party, custom, or in-house systems.

There is, however, a distinction from Apaleo: Mews lets you build against the API freely, but production marketplace integrations go through its partner/certification process.

So I'd characterize them as:

Apaleo = more philosophically/API-native open Mews = more mature ecosystem + still very open

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The question I'd ask vendors

Don't just ask, “Do you have an open API?” Every PMS will say yes.

Ask these instead:

1. Can any customer authorize any third-party developer to access their PMS data without that developer becoming an official partner?
2. Can third-party applications write data back, or is the API primarily read-only?
3. Can we create reservations, modify reservations, check guests in/out, post charges, modify rates/inventory, manage profiles and payments via API?
4. Are webhooks available for essentially every important event?
5. Can we create our own integration without going through your marketplace approval process?
6. Do you charge per API call, per integration, or per connected application?
7. Can the hotel itself generate API credentials, or does the PMS vendor have to approve every integration?
8. If we build an internal application, do you claim any rights over it?
9. If you don't have an integration with a vendor we want, can we build it ourselves?
10. Can we export all our operational data if we leave?

That last one is particularly important. “Open API” isn't the same thing as “open platform.”

My recommendation

If you're selecting a PMS specifically around a composable technology stack, I'd run an RFP with:

🥇 Apaleo — if maximum openness and developer freedom are the #1 criterion.

🥈 Mews — if you want openness plus the largest/mature integration ecosystem and a very polished PMS.

I'd actually put those two through a hands-on technical bake-off rather than relying on vendor demos. Give both vendors the same hypothetical stack—CRM, RMS, payments, door locks, guest messaging, accounting, BI/data warehouse, POS, booking engine, custom app—and have your developers build against the sandbox.

The winner should be determined by what your developers can actually accomplish without asking the PMS vendor for permission, not by the number of logos on the marketplace.

apaleo.dev ·

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2. Mews — arguably the best overall choice

mews.com has arguably the strongest combination of open API + huge existing integration ecosystem.

Mews says its Open API can connect to any application, including bespoke/in-house applications, and exposes core PMS functionality.

Its Connector API is general-purpose and covers substantial operational functionality, while Mews also has APIs for booking engines, POS, channel management, etc.

And the marketplace is enormous: Mews currently advertises 1,000+ integrations with no connection fees.

The other important point: you don't necessarily need to find your application in the marketplace. Mews explicitly says its API is open and that developers can connect third-party, custom, or in-house systems.

There is, however, a distinction from Apaleo: Mews lets you build against the API freely, but production marketplace integrations go through its partner/certification process.

So I'd characterize them as:

When looking for the most "open" Property Management System (PMS) with a robust API marketplace to plug in any third-party app, a few industry leaders stand out specifically because they built their entire architecture around being an open platform rather than a walled garden.

The top contenders for the most open, developer-friendly PMS ecosystems depend slightly on your specific sector (hotels vs. short-term/vacation rentals):

• Mews (Best for Hotels & Modern Hospitality): Mews is widely considered the gold standard for an open-architecture hotel PMS. It features the Mews Hospitality Marketplace , which lists hundreds of plug-and-play integrations, backed by a deeply documented Mews API . They explicitly champion an open-API philosophy, meaning if an app isn’t already in their marketplace, their endpoints (covering reservations, booking engines, POS, accounting, and guest experience) make custom integrations remarkably straightforward.
• Cloudbeds (Best for Independent Hotels & Multi-Property Scale): Cloudbeds has heavily invested in its Cloudbeds Marketplace and developer ecosystem. Their Cloudbeds API utilizes modern architecture (including GraphQL, real-time webhooks, a public Postman collection, and staging environments) built explicitly for custom development. It allows you to sync third-party software so cleanly that external tools behave natively inside the platform.
• Guesty (Best for Short-Term Rentals & Aparthotels): If your property mix leans toward short-term rentals, multi-family, or hybrid serviced apartments, Guesty is unmatched in this category. It offers an extensive open API and a rich partner marketplace, and it is famously progressive with tech integration—even offering advanced developer tools and early-stage AI/MCP server endpoints for real-time data connection.

How to Evaluate Which One Is Right For You:

1. Check the Documentation: Look at their public developer docs (e.g., Cloudbeds' Postman collection or Mews' developer portal). A truly open platform will let you test endpoints in a sandbox environment before you sign a contract.
2. Examine Webhook Support: Ensure they offer real-time webhooks rather than just batch REST calls. If an app updates guest data or triggers an event, your other third-party tools need to know about it instantly.
3. Data Sharing / Scoping: Ask their sales/tech team if their API grants bi-directional access to all core fields (guest profiles, financial ledgers, housekeeping statuses) or if certain data points are restricted to their in-house modules.

To help narrow down the exact fit, could you share:

• What type of properties are you managing (traditional hotels, vacation rentals, or a hybrid)?
• Are there specific third-party apps (like a particular CRM, dynamic pricing tool, or smart-lock system) you need to plug in immediately?

If you are looking for the most genuinely open, API-first property management platform (PMS) designed specifically to prevent walled gardens and let you plug in any third-party app or build custom workflows, Apaleo leads the hotel and serviced apartment sector, while Rentvine stands out as the most open option for long-term residential and property management. Traditional legacy platforms heavily gate their APIs behind partner approval, certification walls, or expensive pay-per-call models, whereas API-first architectures expose every core reservation, rate, guest, and financial data point natively via open REST endpoints and webhooks.

Top Open PMS Platforms Compared

• Apaleo (Hotel & Hospitality): Built entirely on a MACH (Microservices, API-first, Cloud-native, Headless) architecture. It features the Apaleo Store with over 250 plug-and-play third-party apps, and allows any developer to immediately self-register a free account and start building via complete OAuth 2.0 and Webhooks APIs.
• Rentvine (Residential & Property Management): Widely recognized as providing one of the few fully open, RESTful APIs in the long-term property management space. Unlike competitors that lock API access behind costly enterprise tiers, Rentvine includes full open API and Zapier integration capabilities across all of its standard plans.
• Cloudbeds (Hospitality & Vacation Rentals): An industry leader with massive integration support. Its marketplace covers accounting, door locks, marketing, and point-of-sale systems, offering extensive endpoints via the Cloudbeds API though with a more curated partner application process than Apaleo.
• Guesty (Short-Term Rentals): Features a robust marketplace with over 260 third-party partners and an open API, alongside an early-adopter edge in supporting modern developer tooling and AI agent connections.

Integration Openness at a Glance

To help narrow down the exact right system for your tech stack, let me know:

• Is your portfolio short-term vacation rentals, traditional residential, or a hotel property?
• Do you plan to code custom internal apps or connect off-the-shelf third-party software?

If by “most open” you mean we want to choose best-of-breed apps ourselves, have deep API access, and avoid being boxed into the PMS vendor’s native ecosystem, I’d put Mews and Apaleo at the top, with Cloudbeds as the strongest marketplace-heavy alternative.

My ranking for openness

🥇 Mews — probably your best overall choice

Mews is probably the answer if your requirement is “give us a PMS, but let us assemble the rest of the technology stack ourselves.”

Mews explicitly positions its API around integrating any bespoke or third-party application. Its Open API covers reservations, guest data, payments, rates, products, charges, etc., and it has real-time webhooks.

More importantly, the Mews Marketplace currently advertises 1,000+ integrations, spanning payments, POS, revenue management, AI, guest experience, accounting, access control, analytics, operations, and more.

The API is also genuinely open from a developer perspective: Mews says the API is free to build against, with certification required if you want your integration listed in the Marketplace.

🥈 Apaleo — arguably the most technically open

Apaleo is the one I'd investigate if your team is very API/integration-oriented.

Apaleo was designed around an API-first, MACH architecture, rather than starting with a traditional PMS and subsequently bolting APIs onto it. It provides REST APIs, webhooks, sandbox environments, and emphasizes that developers can build their own applications around the platform.

So there's an important distinction:

• Mews: probably the strongest combination of openness + huge existing app ecosystem.
• Apaleo: arguably the strongest choice if the API itself is the center of your architecture.

A recent independent 2026 comparison also concluded that Apaleo has the most genuinely open/self-service developer experience among the hotel-native PMSs it evaluated.

🥉 Cloudbeds — strongest if you want a giant marketplace

Cloudbeds is compelling if you want lots of pre-built integrations plus the ability to build your own.

Cloudbeds currently says it has 450+ integration partners on its platform, and its Marketplace covers POS, CRM, payments, accounting, RMS, guest experience, door locks, BI, housekeeping, loyalty, etc.

Its API is also quite substantial: the PMS API exposes reservations, guests, rooms, check-in/out, POS and other core functions, with separate Data Insights and Accounting APIs.

One caveat: Cloudbeds' API access can depend on the property's package and may be an additional-cost feature, so I'd specifically negotiate this during procurement.

The key distinction I'd make

If you're evaluating PMSs for a modern, composable technology architecture, don't just ask:

“How many integrations do you have?”

Ask:

“Can we access essentially every object and workflow through APIs, webhooks, and standard authentication without asking your professional-services team for permission?”

That's where the platforms diverge.

I'd score them roughly:

Mews:
Open API + huge marketplace + mature hotel functionality = best overall

Apaleo:
API-first architecture + maximum composability = best for a technology-driven organization

Cloudbeds:
Excellent API + huge marketplace + more conventional all-in-one PMS = best middle ground

If this were my RFP

I'd make Mews vs. Apaleo the two finalists and use Cloudbeds as the third benchmark.

And I would test them with 10 actual integrations/workflows you expect to need, rather than relying on vendor claims. For each PMS, test whether you can independently:

1. Read/write reservations
2. Create/update guest profiles
3. Access folios and transactions
4. Post charges
5. Handle payments
6. Access room/inventory status
7. Modify rates/availability
8. Receive real-time webhooks
9. Create a new integration without vendor engineering
10. Get the integration into production without a bespoke commercial agreement

If you tell me what type of property you operate (hotel, resort, extended stay, hostel, etc.) and roughly how many rooms/properties, I can do a deeper Mews vs. Apaleo vs. Cloudbeds comparison—including API limitations, webhooks, marketplace size, integration approval, data ownership, pricing model, and which one gives you the least vendor lock-in.

If your priority is maximum openness + the ability to plug in almost any third-party app, I would look first at API-first PMS platforms, not necessarily the biggest legacy PMS vendors.

My shortlist:

My ranking for “we want to build our own stack and avoid lock-in”:

1. Apaleo — best pure API-first choice

   • Think of it as a PMS core where you assemble your own ecosystem.
   • Best if you have a tech team, multiple properties, automation ambitions, or want custom workflows.

2. Mews — best balance of openness + mature hospitality ecosystem

   • Strong choice if you want many ready-made integrations but still want API control.

3. Cloudbeds — best if you want openness but also a more complete out-of-the-box hotel platform

   • Good for independents, boutique groups, hostels, and properties that do not want to build everything themselves.

4. Oracle OPERA Cloud — best if you are an enterprise chain

   • Massive ecosystem, but less “developer playground” and more “enterprise integration platform.”

For your specific requirement — “plug in any third-party app we want” — I would evaluate vendors on these questions:

• Is the API publicly documented?
• Can developers get sandbox access without a sales process?
• Are there webhooks (real-time events), not just polling?
• Can you read/write:
  • reservations
  • guest profiles
  • rates/inventory
  • payments
  • folios/accounting
  • housekeeping
  • tasks/workflows
• Can you build a private integration without becoming a certified marketplace partner?
• Do you own your data and have bulk export capability?

If I were selecting a PMS for a new tech-forward hotel group, I would start with Apaleo vs Mews, then use Cloudbeds if operational simplicity matters more than architectural purity.

When looking for the "most open" Property Management System (PMS) with a robust marketplace and open API, the industry generally splits into two categories: API-first/MACH-architecture platforms (built from scratch to be plugged into anything) and enterprise/scale-up all-in-ones (which feature massive, mature marketplaces).

The top contenders depending on your exact architecture philosophy include:

• Apaleo (The Truest API-First Open Platform): Widely recognized as the pioneer of the truly open, API-first PMS. Built on a modern MACH architecture (Microservices, API-first, Cloud-native, Headless), Apaleo doesn't even try to do everything natively. It has no built-in booking engine or channel manager by default—instead, it expects you to plug in best-in-class components via the Apaleo Store or build your own custom solutions using their completely self-serve, well-documented APIs with zero integration or gating fees.
• Mews (Best Balance of Out-of-the-Box and Open): Mews is heavily praised for having one of the most vibrant, automation-first marketplaces in the industry. It features an extensive Mews Marketplace packed with hundreds of plug-and-play third-party apps (for POS, accounting, door locks, and upselling) alongside a very robust, developer-friendly open API if you need to custom-code a unique connection.
• Cloudbeds (Most Versatile Marketplace): If you want an all-in-one system that doesn't sacrifice third-party flexibility, Cloudbeds has one of the largest hospitality marketplaces available. Their Cloudbeds Marketplace connects to dozens of third-party solutions, and they back it up with an open API for custom developer modules and workflows.
• Guesty (Best for Short-Term/Mixed Rentals): If your property portfolio leans toward vacation rentals or serviced apartments, Guesty’s entire corporate philosophy is built around opening its platform to external tools. It features a heavily documented open API and a massive ecosystem of specialized short-term rental partners.
• Oracle OPERA Cloud / OHIP (The Enterprise Heavyweight): If you are operating at an enterprise scale, Oracle exposes over 3,100 REST operations via the Oracle Hospitality Integration Platform (OHIP) . It has an enormous marketplace, though it is worth noting that unlike Apaleo's self-serve developer freedom, Oracle typically gatekeeps or monetizes enterprise-level API calls and partner tiers.

To help narrow down which platform fits your tech stack, let me know:

• Are you managing traditional hotels, vacation rentals , or a hybrid model?
• Do you have an in-house development team building custom apps, or do you prefer pre-integrated marketplace apps?

If you want a truly open property management platform with a developer-first approach and zero resistance to plugging in custom or third-party apps, Apaleo and Mews stand out as the most open systems on the market.

The top contenders for an open API marketplace and flexible tech stack architecture break down as follows:

• Apaleo (The most genuinely open/API-first ): Built entirely on a MACH architecture (microservices, API-first, cloud-native, headless), Apaleo is purpose-built for operators who want total control over their tech stack. Any developer can spin up a free account and immediately start building against their complete REST API. The catch? It ships with no native booking engine or channel manager—you have to build or plug in your entire operational stack via the Apaleo Store.
• Mews (Best balance of open API + massive marketplace ): Mews is heavily automation-focused and features a massive marketplace with over 1,0 0 0+ pre-integrated apps alongside a completely open, cloud-native API. If an app isn’t already in their ecosystem, their robust documentation allows your team to hook it up programmatically without jumping through old-school certification hoops.
• Cloudbeds (Best for independent scale & out-of-the-box utility ): While traditionally an all-in-one system (combining PMS, booking engine, and channel manager), Cloudbeds features an extensive Cloudbeds Marketplace and a flexible open API that lets in-house developers build custom modules and connect external software smoothly.
• Oracle OPERA Cloud (Enterprise scale via OHIP ): Exposes over 3,100 REST operations through the Oracle Hospitality Integration Platform (OHIP). It is undeniably powerful for massive global hotel groups, but unlike Apaleo, it gates some advanced access and bills on a pay-as-you-go transaction model per API call.

To help narrow down which of these fits your engineering and operational setup, let me know:

• Are you looking to build completely custom proprietary apps in-house, or do you just need easy access to commercial third-party tools?
• What type of property (hotels, vacation rentals, multi-property group) are you managing?

If by “most open” you mean “the PMS should be the system of record, while we can bolt on almost anything else through APIs/apps without being boxed into the vendor’s ecosystem,” my top pick is Apaleo.

My ranking for API openness

🥇 Apaleo — the one I'd investigate first

Apaleo is unusually explicit about being an API-first PMS rather than an all-in-one suite. Its APIs cover reservations, finance, payments, distribution, profiles, inventory, rate plans, settings, webhooks, identity/OAuth, and even UI extensions.

More importantly for your requirement, Apaleo says its APIs are available to third-party apps and currently advertises 200+ apps/integrations in the Apaleo Store. It explicitly encourages customers to build their own integrations when an app isn't already there.

That's a fundamentally different philosophy from a traditional PMS:

PMS = core hotel operating system
Everything else = interchangeable applications around it

It also provides a developer sandbox and REST APIs, which is a big plus if you're evaluating whether your own technology stack can live on top of it.

🥈 Mews — probably the strongest alternative

Mews has a very good modern API ecosystem. Its Open API includes a general-purpose Connector API plus dedicated APIs for POS, booking engines and channel managers, and it has a formal Marketplace/integration certification process.

I'd choose Mews over Apaleo if you want a more mature, comprehensive PMS that already does more operationally out of the box.

🥉 Cloudbeds — excellent marketplace, somewhat less “open by philosophy”

Cloudbeds has a substantial integration marketplace and its API lets partners build integrations and make them available through the marketplace. Its API covers core PMS resources such as reservations, guests, rooms and house accounts, with additional APIs for things like reporting and accounting.

The distinction I'd make is:

Apaleo: “Here is an open platform; compose your hotel tech stack.”
Mews: “Here is a modern PMS with a very strong integration ecosystem.”
Cloudbeds: “Here is a PMS with a large marketplace and API.”

The important distinction

I wouldn't select based simply on number of marketplace apps.

If you're building a technology stack where you might say:

“We want our own CRM, payments, revenue management, guest messaging, door locks, BI, booking engine, loyalty, POS, AI agent, etc., and we don't want the PMS vendor dictating which ones we use.”

then I'd evaluate Apaleo first.

The questions I'd put to each vendor are:

1. Can every core PMS object be read and written through API?
2. Are booking creation/modification/cancellation all API-accessible?
3. Are there webhooks for every important event, rather than polling?
4. Can third parties access payments/folios/accounting, or are those locked down?
5. Is API access included in the normal subscription, or are capabilities/payments gated by tier?
6. Can any developer build an integration, or does the vendor have to approve it?
7. Can we publish a private/internal app without going through marketplace certification?
8. Can apps extend the PMS UI, not just exchange data?
9. Is there a sandbox with realistic data?
10. Are API rate limits and commercial terms reasonable at scale?

On those criteria, Apaleo is the one that most closely resembles an “operating system for hospitality” rather than a conventional PMS.

If you tell me what type/size of properties you're operating (e.g. 50-room boutique hotel, 500-room resort, multi-property, serviced apartments) and the apps you already know you need, I can do a deep Apaleo vs. Mews vs. Cloudbeds comparison specifically on API openness, write access, webhooks, marketplace breadth, and integration restrictions.