Choose Microsoft SQL Server if your business already runs on Microsoft and wants one vendor for the database, its tools and Azure, and you're happy to license Standard or Enterprise for bigger production systems. Choose PostgreSQL if you want a free, open source database that's the same software whatever you use it for, under a liberal licence. Both have a free route, but they're not equal: SQL Server 2025 Express is free for production use with a 50 GB database limit and the lesser of 1 socket or 4 cores, while PostgreSQL's whole project is free.
I read Microsoft's SQL Server 2025 page, its editions and features documentation, the downloads page and the SQL Server on Linux overview, then PostgreSQL's about, licence and versioning pages. The editions table is where the real decision sits.
SQL Server and PostgreSQL side by side
| SQL Server | PostgreSQL | |
|---|---|---|
| Maker | Microsoft | The PostgreSQL Global Development Group |
| Current release | SQL Server 2025 | PostgreSQL 18 in the current docs |
| Free option (as of October 2026) | Express for production with limits, Developer editions for dev and test only | The whole project, free and open source |
| Paid editions | Standard and Enterprise | None; it's one open source project |
| Express limits | 50 GB database, lesser of 1 socket or 4 cores, 1,410 MB buffer pool | Not applicable |
| Operating systems | Windows, plus Linux since SQL Server 2017, and containers | All major operating systems |
| Licence | Microsoft licensing by edition | PostgreSQL License, similar to BSD or MIT |
Where the free SQL Server editions stop
Microsoft describes SQL Server Express as the entry-level, free database, ideal for learning and for building desktop and small server data-driven applications. Its scale limits are the catch: the SQL Server 2025 editions page caps Express at the lesser of 1 socket or 4 cores, 1,410 MB of buffer pool memory and a maximum relational database size of 50 GB.
The Developer editions are different. Enterprise Developer and Standard Developer include all the features of their paid editions but are licensed only for development and testing, not as production servers. Standard itself is limited to the lesser of 4 sockets or 32 cores and 256 GB of buffer pool memory, while Enterprise goes up to the operating system maximum. So as a business grows, it moves up Microsoft's edition ladder, whereas PostgreSQL has no ladder to climb.
What SQL Server 2025 adds
Microsoft's pitch for SQL Server 2025 leans hard on AI. It lists semantic search combined with full-text search, integrated vector embedding and interfaces for AI models running locally or in the cloud. Developers get a native JSON type with its own index and functions, regular expressions, the ability to connect data to any REST interface and change event streaming for event-driven apps. You can also mirror data into Microsoft OneLake through Fabric and sign in with Microsoft Entra managed identity.
Linux support is real but has gaps. SQL Server has run on Linux since SQL Server 2017 using the same database engine as on Windows, and the 2025 release supports Red Hat Enterprise Linux and Ubuntu, but Microsoft says SUSE Linux Enterprise Server isn't supported on SQL Server 2025 and later.
Why PostgreSQL appeals to growing teams
PostgreSQL is released under the PostgreSQL License, which its project calls a liberal open source licence similar to BSD or MIT, and the licence page says there are no plans to change it: the group remains committed to keeping PostgreSQL free and open source in perpetuity. It's highly extensible, so you can define your own data types, build custom functions and write code in different languages without recompiling the database.
It also takes standards seriously. Version 18 conforms to at least 170 of the 177 mandatory features for SQL:2023 Core conformance, and the project notes that no relational database meets full conformance yet. Each major version gets five years of support.
Which one suits you
- Do your apps, reports and staff already live in the Microsoft world and Azure? SQL Server keeps everything under one roof.
- Will your database pass 50 GB soon? Express won't cover it, so it's Standard, Enterprise or PostgreSQL.
- Want vector search inside the database from the vendor? SQL Server 2025 builds it in.
- Would you rather avoid edition and core limits altogether? PostgreSQL has a single free build.
- Running SUSE Linux? Check Microsoft's support list first, because SQL Server 2025 doesn't support it.
If you're already planning a switch, read my notes on using a database migration service, and for the wider Microsoft toolkit see these Microsoft 365 tools for small business productivity.
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My advice on SQL Server or PostgreSQL
If you're a Microsoft shop with Windows servers and staff who already know SQL Server Management Studio, staying on SQL Server is the low-risk choice, and Express is a free start for small apps. If you're building something new and want to keep your options open across clouds and operating systems, I'd go with PostgreSQL. The trigger to watch is size: plan your next step well before an Express database nears its 50 GB ceiling, not the week it hits it.
Do you make database tools? Tool makers can ask to be considered for a featured place in comparisons like this one.
Frequently asked questions
Is SQL Server free?
SQL Server 2025 Express is free and can run in production for desktop, web and small server apps, within its limits. The Developer editions are free but licensed only for development and testing.
What is the SQL Server Express database size limit?
Microsoft's SQL Server 2025 editions page lists a maximum relational database size of 50 GB for Express, plus a compute cap of the lesser of 1 socket or 4 cores.
Does SQL Server run on Linux?
Yes, since SQL Server 2017. SQL Server 2025 supports Red Hat Enterprise Linux and Ubuntu, but not SUSE Linux Enterprise Server.
Is PostgreSQL free for commercial use?
Yes. The PostgreSQL License lets you use, copy, modify and distribute it for any purpose, and the project says it'll stay free and open source in perpetuity.
Does PostgreSQL have editions like SQL Server?
No. PostgreSQL is one free, open source project rather than a set of paid editions, and each major version is supported for five years.
