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Updated and tested 17 October 2026
The installer is the straightforward half of this. Work through the wizard and you end up with a running instance. The download page is where it goes wrong, because several buttons say some version of "free" and they mean different things once you are in production, and you find out which one you picked during a licence review.
Which download first, then the wizard in outline, then the unattended command line for building more than one machine, then the post-install steps the wizard does not do for you.
Which mssql download you need
The Microsoft mssql download page lists the free editions. Standard and Enterprise are bought through volume licensing or a cloud subscription and there is no button for them. You download mssql server media once and that same ISO installs any of them. Edition is decided by the product key or by the edition you choose during setup, which is why an Evaluation install can be converted later without reinstalling anything.
Developer edition
Full Enterprise functionality, no cost, licensed for development and test only. That last clause is the whole story: run Developer on a machine that serves real users and you are out of compliance, however small the database is. The downloads page now splits it into a Standard flavour and an Enterprise flavour, which is new and catches people who last downloaded it a few years ago. Pick the flavour matching the edition you intend to buy for production, otherwise your dev box has features your production box will not.
Express edition
Free for production, with limits. Compute is capped at the lesser of one socket or four cores, the buffer pool is capped at 1,410 MB per instance and the maximum size of a single relational database moved from 10 GB to 50 GB in SQL Server 2025. The full comparison of Express and Developer covers what each one costs you in the other direction. Most of what you will read online still says 10 GB, so the 50 GB figure bears repeating. It makes Express a reasonable choice for a small line-of-business app, though the memory ceiling bites long before the size ceiling does.
Evaluation edition
Enterprise functionality on a timer. It is what I install when I am proving something works before anyone signs a purchase order, and the edition upgrade path in setup converts it to a licensed edition in place. Keep the complete edition and component matrix open while you decide. Standard's limits moved in 2025 to the lesser of 4 sockets or 32 cores and a 256 GB buffer pool.
Run the installation wizard
To install mssql server on Windows you mount the ISO, run setup.exe and land in the SQL Server Installation Center. The path through it is short. Installation, then "New SQL Server standalone installation", then the licence terms, then your edition or product key, then the Feature Selection page. Database Engine Services is the only feature most installs need, and everything else adds services you then have to patch.
Two pages take more than a click-through. Instance Configuration decides default versus named. Database Engine Configuration sets the authentication mode, the sysadmin accounts and, on the Data Directories tab, where your data and log files land. Moving those later is tedious, so it is the screen to slow down on.
One documented warning catches people installing on a remote machine. Setup run from local client media over a Remote Desktop session can fail, and the installation guide recommends media local to the target machine or on a network share. Copy the ISO across first.
Unattended install with setup.exe
Once you've built the same box twice, do it from the command line. Microsoft's own example, verbatim from the command prompt install reference:
setup.exe /q /ACTION=Install /FEATURES=SQL /INSTANCENAME=MSSQLSERVER /SQLSVCACCOUNT="<DomainName\UserName>" /SQLSVCPASSWORD="<password>" /SQLSYSADMINACCOUNTS="<DomainName\UserName>" /AGTSVCACCOUNT="NT AUTHORITY\NETWORK SERVICE" /SQLSVCINSTANTFILEINIT="True" /IACCEPTSQLSERVERLICENSETERMSWhat the ones that matter are doing:
/IACCEPTSQLSERVERLICENSETERMSis required. Setup won't proceed without it in unattended mode./FEATUREStakes a comma-delimited list with no spaces, drawn fromSQLEngine,Replication,FullText,AS,RS,IS,Conn,Tools,PolyBaseand a few others.SQLis the shorthand parent that pulls in the engine and its children./INSTANCENAMEisMSSQLSERVERfor a default instance, anything else for a named one./SQLSYSADMINACCOUNTSprovisions the sysadmin logins and is required for every non-Express edition. Forget it and setup fails a rule check rather than silently installing something you can't administer./SECURITYMODE=SQLturns on mixed mode, and/SAPWDis mandatory whenever you pass it./Qis fully silent,/QSshows progress with no interaction and/Qwins if you pass both.
Notice what Microsoft's example does not include: /SECURITYMODE. That install comes out in Windows Authentication mode. The engine-only mixed-mode equivalent, composed from the same parameter table, is this:
setup.exe /Q /ACTION=Install /FEATURES=SQLENGINE /INSTANCENAME=MSSQLSERVER /SQLSYSADMINACCOUNTS="BUILTIN\Administrators" /SECURITYMODE=SQL /SAPWD="<StrongPassword>" /TCPENABLED=1 /IACCEPTSQLSERVERLICENSETERMS/TCPENABLED=1 switches on the TCP/IP protocol at install time. Without it, a fresh install accepts local connections and refuses every remote one, and the fix afterwards is Configuration Manager plus a service restart.
