KB: DRC HTML Output empty when path is too long
Created: October 07, 2025 | Updated: October 07, 2025
Altium Designer
When generating a Design Rule Check (DRC) report in Altium Designer, users may encounter a blank HTML output even though the DRC command executes successfully and batch rule checkboxes are enabled. This issue is typically caused by the file path exceeding Windows' maximum path length limitation of 256 characters. Relocating the project to a shorter path resolves the issue and allows the report to generate correctly.
Solution Details
DRC Report HTML File Is Blank After Generation
Why the DRC Report Appears Blank
The blank HTML report is not due to missing rules or rendering issues, but rather a Windows operating system limitation. If the full path to the generated report exceeds 256 characters, the system fails to write the content properly, resulting in an empty file.
What to Do
• Shorten the project file path.
• Move the project to a location with a shorter directory structure.
How to Do It
1. Check the Current Project Path
- Locate the folder where the DRC report is being saved.
- Right-click the HTML file and select Properties to view the full path.
2. Move the Project to a Shorter Path
- Copy the entire project folder to a location like
C:\AltiumProjects\. - Open the project from the new location in Altium Designer.
3. Regenerate the DRC Report
- Go to Tools » Design Rule Check.
- Ensure all necessary rule checkboxes are ticked.
- Run the DRC report command again.
4. Verify the HTML Output
- Open the newly generated HTML file.
- Confirm that the report content is now visible.
Additional Notes
- This issue is specific to Windows environments due to the 256-character path limit.
- For more information, refer to Altium’s documentation: Support for Long Path Names.