Solidworks Host File Block Hot! May 2026
SolidWorks relies on a licensing system that often needs to "phone home" to a server. Sometimes, users or third-party scripts modify the Windows Hosts file to block these connections, which can lead to activation errors, crashes, or "License client lost" messages. The Day the Design Office Stood Still
Alex sat at his desk, ready to finalize the assembly for the new drone prototype. He double-clicked the SolidWorks icon. He waited. Instead of the familiar splash screen, a cold, grey box appeared:"Could not obtain a license for SOLIDWORKS. System Clock Check Failed or Licensing Service is unavailable."
Alex knew his internet was fine. He knew the company server was up. He remembered a "performance hack" he had found on a forum the night before—a script that supposedly sped up load times by blocking "unnecessary background pings." The Hidden Gatekeeper
What Alex hadn't realized was that the script had edited his Hosts file. This file is like a private phone book for your computer; it tells Windows exactly where to find specific internet addresses before it even asks a DNS server.
By adding lines like 127.0.0.1 ://solidworks.com, the script had told Alex’s computer that the SolidWorks licensing server was actually inside his own machine. When SolidWorks tried to verify his seat, it hit a digital brick wall. The Restoration To fix it, Alex had to perform a bit of "digital surgery":
Locate the File: He navigated to C:\Windows\System32\drivers\etc.
Gain Permission: He opened Notepad as an Administrator, then dragged the hosts file into the window.
The Purge: He looked for any lines containing "SolidWorks" or "Flexnet." He saw a dozen entries redirecting traffic to 0.0.0.0 or 127.0.0.1.
Clean Slate: He deleted those lines, saved the file, and restarted his computer. The Lesson
When Alex restarted SolidWorks, the software reached out, found the genuine server, and blossomed into life. He learned that while "blocking pings" might sound like a shortcut to speed, it usually just cuts the lifeline the software needs to function. 🛠️ Common Signs Your Hosts File is Blocked
Activation Errors: "Failed to connect to the activation server."
Startup Hangs: The splash screen stays visible for minutes before failing. FlexNet Errors: Error codes like -15, 10 or -8, 544. 💡 Pro-Tips for Troubleshooting
Check for "Read-Only": Right-click the hosts file > Properties. Ensure "Read-only" is unchecked before saving.
Anti-Virus Interaction: Sometimes, your AV software will "protect" the hosts file and revert your changes. Disable it temporarily while editing.
Standard DNS: If the file is clean but it still fails, try flushing your DNS cache by typing ipconfig /flushdns in the Command Prompt.
Walk through the specific license server port numbers (25734/25735) to check your firewall? Troubleshoot a specific error code you are seeing?
The "SolidWorks host file block" usually refers to a technical workaround used to fix connection issues between a client computer and a SolidWorks PDM (Product Data Management) server. This is necessary when your computer’s DNS (Domain Name System) cannot properly resolve the server's name to its IP address. Purpose of the Host File Block Solidworks Host File Block
DNS Workaround: Bypasses faulty network name resolution by manually "hard-coding" the server's IP address to its name on your local machine.
PDM Connectivity: Ensures the PDM client can find the Archive Server and Database Server to check files in and out.
Installation Fixes: Sometimes used to prevent "blank" installation screens caused by the firewall or browser blocking necessary HTML files. Detailed Step-by-Step Configuration
To implement this "block" (which is actually an entry in the Windows hosts file), follow these steps: Open Notepad as Administrator: Click the Start menu and type "Notepad."
Right-click it and select Run as Administrator (this is critical for saving changes). Navigate to the Hosts File: In Notepad, go to File > Open. Browse to: C:\Windows\System32\drivers\etc\.
Change the file type dropdown from "Text Documents (.txt)" to **All Files (.*)**. Select the file named hosts and click Open. Add the Server Entry:
Scroll to the bottom of the file (below any lines starting with #).
Enter the Server IP Address, hit TAB, and then enter the Server Hostname. Example: 192.168.1.100 SRV-PDM01. Save and Flush DNS: Save the file and close Notepad. Open a Command Prompt (type cmd in Start).
Type ipconfig /flushdns and press Enter to force Windows to recognize the new entry. Common Troubleshooting Scenarios
Permission Denied: If you get a "permission denied" error, you did not run Notepad as an Administrator.
Firewall Blocking: If the host file is correct but connection fails, you may need to create an Inbound Rule in the Windows Defender Firewall for ports 3030 (Archive), 1433/1434 (SQL), and 25734/25735 (License).
Blank Installer: If you are trying to install and the screen is blank, right-click the installation HTML files (e.g., frameset.html) and check Unblock in the Properties menu. Retired - SOLIDWORKS Forums
Users often modify the Windows hosts file to prevent SolidWorks from communicating with its home servers. This is sometimes used for privacy or to manage software activation locally.
The Logic: By mapping a software's activation or telemetry URL to a "dead" IP address like 0.0.0.0 or 127.0.0.1, you effectively cut off the application's ability to reach that site.
Alternative Method: Experts often recommend using the Windows Defender Firewall for this instead, as it is easier to manage and less likely to be bypassed by modern Windows security features. 2. Resolving PDM Connectivity (The "Positive" Block)
In a professional setting, editing the hosts file is a common workaround when your computer cannot "find" the server hosting your SOLIDWORKS PDM (Product Data Management) vault. SolidWorks relies on a licensing system that often
The Issue: If your DNS (Domain Name System) fails to translate a server name into an IP address, PDM will fail to connect.
The Fix: Adding a manual entry to the hosts file ensures your machine always knows exactly where the server is located. How to Edit the Hosts File
If you need to perform either of these actions, the process is as follows:
Open Notepad as Administrator: Search for Notepad in the Start Menu, right-click it, and select Run as Administrator.
Navigate to the File: Go to File > Open and paste this path: C:\Windows\System32\drivers\etc\. Change the file type dropdown from "Text Documents (.txt)" to **"All Files (.*)"** to see the hosts file. Add Your Entry: To Block: Add a line like 0.0.0.0 license.solidworks.com.
To Connect (PDM): Add a line with the server IP followed by the name, e.g., 192.168.1.100 PDM-SERVER.
Save and Close: Save the file. You may need to restart your browser or SolidWorks for the changes to take effect. 3. SolidWorks "Blocks" (Internal CAD Feature)
It is worth noting that in SolidWorks, a "Block" is also a standard CAD feature used to group sketch entities.
block linked to file - best way to edit the block? | SOLIDWORKS Forums
Part 3: Step-by-Step Guide to Implementing the Block (For Educational Purposes)
Disclaimer: This guide is provided for educational and legacy troubleshooting purposes only. Modifying your hosts file to bypass licensing is a violation of the Dassault Systèmes Software License Agreement.
5. How to Implement (Administrative Procedure)
Step 1: Open Notepad as Administrator.
Step 2: Open the file:
C:\Windows\System32\drivers\etc\hosts
Step 3: Add entries at the bottom (example):
127.0.0.1 sw.activation.dart
127.0.0.1 license.dat
127.0.0.1 events.spatial.com
Step 4: Save the file (no extension).
Step 5: Flush DNS cache:
ipconfig /flushdns
Step 6: Restart SolidWorks.
3. Why Block SolidWorks Network Access?
Legitimate reasons for blocking (in a corporate or managed environment):
| Reason | Description | |--------|-------------| | License Compliance Checks | Prevent the software from continuously phoning home to verify network licenses (can reduce server load). | | Stop Unwanted Updates | Avoid forced updates that may break custom configurations or third-party integrations. | | Data Privacy | Block telemetry or usage data from being sent to Dassault Systèmes (common in sensitive engineering environments). | | Firewall Supplement | Add a lightweight, zero-resource block before traffic reaches the firewall. |
Illegitimate reason (not condoned): Attempting to bypass online activation for pirated versions.
7. Conclusion
Blocking SolidWorks via the Hosts file is a technically simple but increasingly ineffective and legally risky practice. While it may temporarily suppress license checks or telemetry, modern versions of SolidWorks employ multiple countermeasures that render host-based blocking incomplete. For system administrators needing to control SolidWorks network access, proper firewall rules or group policies are superior. For end users, tampering with the Hosts file risks license revocation and software malfunction without providing reliable long-term benefits.
Final recommendation: If you own a legitimate license, do not modify the Hosts file. Contact your VAR or Dassault Systèmes directly for network configuration support. If you do not own a license, purchase one—or explore free alternatives like FreeCAD, Onshape (free tier), or Fusion 360 for personal use.
A "Solidworks Host File Block" usually refers to modifying the Windows
file to prevent the SolidWorks application from communicating with validation or telemetry servers. This is often done to bypass license checks or stop unwanted data collection. 1. Locating the Hosts File
The hosts file is a system file that maps hostnames to IP addresses. C:\Windows\System32\drivers\etc (it has no file extension). 2. Editing the File (Requires Admin Rights)
You cannot save changes to this file without administrative privileges. Start Menu , right-click it, and select Run as Administrator In Notepad, go to File > Open Paste the path C:\Windows\System32\drivers\etc into the address bar.
Change the file type filter (bottom right) from "Text Documents ( .txt)" to **"All Files ( Select the file and click 3. Adding the Blocks
To block SolidWorks from reaching specific servers, you map the server's domain name to your local machine (IP ). Common addresses targeted include: 127.0.0.1 activation.solidworks.com 127.0.0.1 im-node1.solidworks.com 127.0.0.1 im-node2.solidworks.com 127.0.0.1 sldworks-entitlements.solidworks.com
Note: Adding these lines ensures that whenever SolidWorks tries to "call home," the request is rerouted back to your own computer and fails. 4. Verifying the Block Command Prompt in the Start Menu). ping activation.solidworks.com If the block is successful, you should see it pinging rather than an external IP address. 5. Complementary Firewall Blocks
For a "complete" block, users often supplement host file edits with Outbound Rules Windows Defender Firewall Firewall & network protection > Advanced settings Outbound Rules > New Rule and browse to the SLDWORKS.exe file (usually in C:\Program Files\SOLIDWORKS Corp\SOLIDWORKS Block the connection and apply it to Domain, Private, and Public profiles.
Modifying these files to bypass licensing is a violation of the software's Terms of Service. For official support or license management, refer to the SolidWorks SolidNetWork License (SNL) Manager documentation. If you'd like, let me know: Are you trying to block activation Are you using a standalone
Disclaimer: This article is for informational and educational purposes only. Bypassing software licensing agreements (piracy) is illegal and violates SolidWorks’ Terms of Service. This guide is intended for legitimate users who wish to prevent unauthorized external communication from a licensed copy or for network administrators managing firewalls.
6. Limitations & Risks
| Limitation | Explanation | |------------|-------------| | Easily bypassed | SolidWorks can use hardcoded IPs or DNS-over-HTTPS. | | Breaks legitimate functions | Online help, toolbox updates, 3D ContentCentral, and network licensing will fail. | | False security | Gives admin a false sense that all phoning home is blocked (many apps ignore hosts file). | | Legal risk | If blocking is used to avoid paying for licenses, it violates copyright law (DMCA, EUCD). | | Detection | Modern SolidWorks versions may detect hosts file tampering and disable features / show non-compliance warnings. | Part 3: Step-by-Step Guide to Implementing the Block
3. Common Use Cases (Legitimate vs. Illegitimate)
| Context | Legitimacy | Technical Outcome | |--------|------------|-------------------| | Pirated software | Illegal | Prevents online validation checks that would flag a cracked license. | | Corporate lab / air-gapped PC | Potentially allowed (check EULA) | Stops unnecessary outbound connection attempts, reducing firewall logs. | | Privacy-focused user (legit license) | Grey area | Blocks telemetry but may violate license terms. | | Troubleshooting connectivity issues | Legitimate | Temporarily overriding DNS to test local license server resolution. |
For legitimate license holders: Disabling validation can cause SolidWorks to enter "license not found" mode after a grace period (e.g., 30 days). Periodic online checks are required for most network and standalone licenses.