SQL Server 2025 Installation Offline:
Installing SQL Server on a machine without internet access can feel confusing, especially for beginners. Many DBAs and non-technical users struggle when the online installer fails or downloads incomplete files. The good news is that SQL Server 2025 installation offline is simple when you use the ISO file method. In this guide, you will learn how to download the SQL Server 2025 ISO file, prepare your system, and complete the offline installation with confidence.
Why Choose SQL Server 2025 Installation Offline?
Offline installation means you download everything once and install SQL Server without relying on an active internet connection. This method works best for secure environments, servers without internet access, and slow or unstable networks.
- Works on isolated or secure servers
- Avoids download failures during setup
- Saves time when installing on multiple machines
- Gives full control over installation files
For SQL Server DBA beginners, the offline method is also easier to troubleshoot because all files are already available locally.
Install SQL Server 2025 offline step by step:
What You Need Before Starting?
Before you begin the SQL Server 2025 installation offline, make sure your system is ready. Preparing in advance helps you avoid common setup errors.
System Requirements Checklist
- Windows Server or Windows 10/11 (64-bit)
- At least 8 GB RAM (16 GB recommended)
- Minimum 10 GB free disk space
- Administrator access to the system
Also, ensure that Windows updates are completed and the system is restarted before installation.
Required account permission for installation of SQL Server 2025 offline
Please check below table for required access to installation account.
How to Download SQL Server 2025 ISO File?
The most important step in SQL Server 2025 installation offline is downloading the correct ISO file. The ISO contains all setup components required for a complete installation.
Steps to Download the ISO File
- Open a system with stable internet access
- Go to the official Microsoft SQL Server download page
- Select SQL Server 2025 edition (Evaluation, Developer, or Enterprise)
- Choose the option to download the ISO file
- Save the ISO file to a local drive
After the download finishes, verify that the ISO file size matches the details shown on the download page. This helps confirm the file is complete.
Transfer the ISO File to the Offline Server
If your target server does not have internet access, you must copy the ISO file manually.
- Use a USB drive or external hard disk
- Copy the ISO file to the server
- Place it in a folder with enough free space
Once copied, you are ready to begin the SQL Server 2025 installation offline process.
Mount the SQL Server 2025 ISO File
Windows allows you to mount ISO files without extra software. Mounting the ISO makes it behave like a DVD drive.
How to Mount the ISO?
- Right-click on the ISO file
- Select “Mount”
- Open “This PC” and locate the new virtual drive
You will now see the SQL Server setup files inside the mounted drive. (SQL Server 2025 Installation Offline)
Start SQL Server 2025 Offline Installation
With the ISO mounted, you can start the actual installation.
Step-1: Launch Setup
- Open the mounted ISO drive
- Double-click setup.exe
- Allow the application to run as an administrator
The SQL Server Installation Centre will open and guide you through the setup.
Step-2: Choose Installation Type
When prompted, select the correct installation option based on your needs. Here we are going to install a standalone server hence we are going ahead with…
‘New SQL Server standalone installation or add features to an existing installation’
For beginners, a new stand-alone installation is the safest choice.
Step-3: Select Edition of SQL Server 2025
In next window, you have to select an edition of SQL Server to install. You can choose to either use a SQL Server license that you already have or you can put the new licence with new product key. In this example we are going to install a free edition of SQL Server Enterprise Developer which has largest set of SQL Server features.
after selecting the desired edition, click next and check box for ‘License Terms‘. Click next, in new window you will see the progress of ‘Global Rules‘:
The next window will check the ‘Install Rules‘, it will check and identify if there is any problems that might occur while running the setup.
Step-4: Azure Extension for SQL Server
Azure Extension for SQL Server (in SQL Server 2025 setup) is an optional component that connects your SQL Server to Azure so you can use Azure-based management and security features.
In simple terms: It lets Microsoft Azure see and manage your SQL Server (even if it’s on-prem or on a VM).
What it enables?
- Azure Arc integration – manage SQL Server from the Azure portal
- Centralized monitoring & inventory
- Security features like vulnerability assessment and Defender for SQL
- Licensing & update insights
Do you need it?
- Yes, if you want Azure monitoring, security, or Arc features
- No, if your SQL Server is fully on-prem and you don’t use Azure services
It does not affect core SQL Server functionality and can be skipped during setup. (SQL Server 2025 Installation Offline)
Step-5: Select Features Carefully
SQL Server allows you to choose which components to install. Installing only what you need keeps the system clean and efficient.
Recommended Features for Beginners
- Database Engine Services
- SQL Server Management Tools (if included)
- Client Connectivity SDK
You can always add more features later if required.
Step-6: Instance Configuration Explained Simply
An instance is a separate SQL Server environment on your machine.
- The default instance works for most users
- Named instance helps when running multiple SQL Servers
If you are unsure, choose the default instance.
Step-7: Server Configuration Settings
SQL Server services run under specific accounts. Beginners can safely use the default settings.
- Leave service accounts unchanged
- Set SQL Server service startup type to Automatic
This ensures SQL Server starts automatically after a system reboot.
In the ‘Collation‘ tab, you can select collation as per your requirement. We are going ahead with the default collation:
SQL_Latin1_General_CP1_CI_AS
Step-8: Database Engine Configuration
This step controls how you connect and secure SQL Server.
1. Authentication Mode
- Windows Authentication (recommended)
- Mixed Mode (requires SQL login password)
We are selecting Mixed Mode as it will support for both windows and SQL login logins as well.
Add SQL Server Administrators:
- Click “Add Current User”
- Confirm your user account is listed
This prevents permission issues after installation.
2. Data Directories
Set the root directory for SQL Server 2025 offline installation. You can also set the System database, User database, User database log and Backup directory in Data Directories tab.
3. TempDB
TempDB is a shared workspace used by SQL Server for sorting, temporary tables, and queries. Proper configuration avoids performance issues later.
What you configure?
- Number of data files – usually set equal to CPU cores (up to 8) to reduce contention
- Initial file size – pre-allocate space to avoid frequent auto-growth
- Auto-growth settings – use fixed MB growth instead of percentage
- File location – place TempDB on fast storage if possible
Good TempDB settings improve performance and prevent common bottlenecks.
Configuring TempDB during installation saves time and avoids post-install changes.
Best-practice TempDB configuration:
| Configuration | Recommended Setting | Comments |
|---|---|---|
| Number of data files | Equal to logical CPU cores (max 8) | Start with 4–8 files; increase only if needed |
| Data file size | 8 GB per file | All data files must be the same size |
| Log file size | 8–16 GB | Depends on workload |
| Data file auto-growth | 512 MB (fixed) | Avoid percentage growth |
| Log file auto-growth | 512 MB – 1 GB (fixed) | Prevent frequent growth events |
| File location | Fast storage (SSD / Premium disk) | Separate from user DBs if possible |
| Instant File Initialization | Enabled | Improves file growth performance |
| Pre-allocation | Yes | Avoids auto-growth during peak usage |
| Configuration timing | During installation | Prevents post-install changes |
Typical production example
- 16 CPU cores → 8 TempDB data files
- Each data file: 8 GB, growth 512 MB
- Log file: 16 GB, growth 1 GB
4. MaxDOP
MaxDOP (Maximum Degree of Parallelism) controls how many CPU cores SQL Server can use for a single query.
Use this rule:
MaxDOP = number of logical cores per NUMA node
with these limits:
- Maximum value: 8
- Minimum value: 1
Common Scenarios:
| Server CPU layout | Recommended MaxDOP |
|---|---|
| 4 cores total | 4 |
| 8 cores total | 8 |
| 16 cores, 1 NUMA node | 8 |
| 32 cores, 2 NUMA nodes (16 each) | 8 |
| 64 cores, 4 NUMA nodes (16 each) | 8 |
5. Memory
Simple memory configuration for SQL Server 2025, suitable for most production environments:
Never leave Memory to unlimited, use given below simple rule of thumb to setup the memory.
| Total RAM | Leave for OS | Set Max Server Memory |
|---|---|---|
| <_ 16 GB | 4 GB | Total RAM – 4 GB |
| 16-64 GB | 6-8 GB | Total RAM – 6/8 GB |
| > 64 GB | 8-12 GB | Total RAM – 8/12 GB |
But in this example we are going with default settings.
Complete the Offline Installation
After reviewing all selections, start the SQL Server 2025 installation offline.
- Click Install
- Wait for the setup to complete
- Do not close the installer during the process
The installation may take several minutes, depending on system speed. Finally, your SQL Server 2025 installation completed successfully.
Verify SQL Server Installation
Once setup finishes, confirm that SQL Server works correctly.
- Open SQL Server Configuration Manager
- Check SQL Server service status
- Connect using SQL Server Management Studio
A successful connection confirms the offline installation worked.
Common Problems and Simple Fixes
Even with offline installation, some issues may appear.
Setup Fails During Installation
- Restart the system
- Run setup as administrator
- Disable antivirus temporarily
Cannot Connect After Installation
- Ensure SQL Server service is running
- Check authentication mode
- Confirm firewall settings
These fixes solve most beginner issues.
Practical Tips for SQL Server DBA Beginners
- Keep the ISO file for future installations
- Document instance and authentication details
- Apply service packs and updates later when online
- Practice basic backups immediately
Good habits early make database management easier later.
Final Thoughts
SQL Server 2025 installation offline using the ISO file is reliable, secure, and beginner-friendly. By downloading the ISO once and following a structured setup process, you avoid common online installer issues. This approach works perfectly for secure servers, labs, and production environments. With SQL Server installed successfully, you can now focus on learning database management and building confidence as a SQL Server DBA.
Read More:
Offline Installation of SSMS 22 | Step-by-Step Guide for DBAs