Solidworks Host File Block Fix May 2026

The hosts file is a plain text file that maps hostnames to IP addresses. By adding lines like: 127.0.0.1 license.solidworks.com ...you are telling your computer to "look" for the SolidWorks license server on your own hard drive instead of on the internet.

In theory, this prevents SolidWorks from "phoning home" to check if your license key is valid or if it has been blacklisted.

The hosts file is a plain text file that maps hostnames to IP addresses. When you type a web address, your PC checks this file before asking the internet's DNS servers. solidworks host file block fix

How it relates to SolidWorks: SolidWorks background processes (e.g., sldworks_fs.exe, SWLicensingService) periodically check in with Dassault Systèmes’ activation servers. By editing the hosts file, you redirect those server names to a dead end (usually 127.0.0.1 – your own computer).

Before you can fix the issue, you must understand the battlefield. The hosts file is a plain text file found in every operating system (Windows, macOS, Linux) that maps hostnames to IP addresses. Think of it as a local, manual GPS override for your internet traffic. The hosts file is a plain text file

Remove or comment out suspicious lines by placing a # at the start or delete them. Example: #127.0.0.1 swlicensing.solidworks.com

You added the lines, but SolidWorks still gives you an error. Here is why.

This is the pure "Host File Block Fix" for 90% of users. Remove or comment out suspicious lines by placing

Warning: Editing system files requires administrator privileges. Do this on a domain-joined PC only if you have local admin rights.

Procedure:

Delete only those specific lines. Do not delete the # localhost line.

Save the file (Ctrl+S).

Go back to Properties and re-check "Read-only" (This prevents future malware from hijacking it).