CTB to TXT Converter

CTB to TXT Conversion Explained

Converting .CTB to .TXT extracts the binary color-mapping data from an AutoCAD Color-Dependent Plot Style Table into a human-readable plain text file. People convert these files to document, audit, or compare CAD plotting standards outside of drafting software.

When you convert .CTB to .TXT, you gain universal readability and the ability to track changes using standard text-based version control. However, you lose all functional utility. A .TXT file cannot be used by CAD software to plot drawings. You trade a functional configuration file for a static documentation file. If your goal is to plot or share a working plot style with another drafter, this conversion is a bad idea.

Typical Tasks and Users

This conversion is highly specific to CAD administration and quality assurance. Common users include:

• CAD Managers: Documenting company plotting standards (lineweights, screening, and linetypes) for internal manuals.
• BIM Coordinators: Comparing two different .CTB files to find discrepancies in color mappings from external contractors.
• Software Developers: Extracting legacy CAD standards to migrate them into new systems or databases.
• Quality Assurance Teams: Storing plot style configurations in Git repositories to track unauthorized changes over time.

Software & Tool Support

Because .CTB is a proprietary binary format, direct conversion options are limited.

• Autodesk AutoCAD: Natively creates and edits .CTB files via the Plot Style Table Editor, but does not offer a direct "Save As TXT" feature.
• AutoLISP Scripts: CAD managers often write custom LISP routines within AutoCAD to iterate through the 255 index colors and write the properties to a .TXT or .CSV file.
• Third-Party Utilities: Standalone tools like CTB Print or custom Python parsers can read the binary structure and output text.
• Text Editors: Once converted, tools like Notepad++ or Visual Studio Code are used to view, search, and compare the resulting .TXT files.

Pros and Cons of the Conversion

Pros:

• Universal Compatibility: Anyone can open a .TXT file on any operating system without an AutoCAD license.
• Transparency: It exposes the exact lineweight, dither, grayscale, and screening values for all 255 AutoCAD Index Colors (ACI) in a readable list.
• Version Control: Plain text files work perfectly with Git or SVN, allowing teams to see exactly which color mapping changed between versions.

Cons:

• Loss of Functionality: AutoCAD cannot read a .TXT file to plot or publish drawings.
• One-Way Process: Converting a .TXT file back into a functional .CTB file is difficult and requires specialized scripting.
• Formatting Loss: Plain text lacks the visual, tabbed graphical user interface of the native AutoCAD Plot Style Editor.

Conversion Difficulties & Why Convert.Guru

The main technical difficulty in converting .CTB to .TXT is decoding the proprietary binary structure. A .CTB file is not a text file; opening it directly in a text editor displays garbled characters. A proper conversion tool must parse specific byte offsets to extract the properties for all 255 colors, including pen numbers, virtual pens, screening percentages, linetypes, and end/join styles. Simple text extraction tools fail completely on this format.

Convert.Guru handles this conversion accurately by decoding the binary CAD data and mapping it into a clean, structured .TXT file. It formats the 255 color mappings into an organized list or tabular structure, ensuring no lineweight or screening values are lost, all without requiring an AutoCAD installation or custom AutoLISP scripts.

CTB vs. TXT: What is the better choice?

Which format should you choose?

Choose .CTB when you are actively drafting, plotting, or publishing drawings in AutoCAD. It is the only format that will actually control how your lines print on paper or export to PDF.

Choose .TXT when you need to document your CAD standards, share plot settings with non-CAD users, or track configuration changes in a repository. Avoid this conversion entirely if you simply need to send a plot style to another drafter—send the original .CTB file instead.

Conclusion

Converting .CTB to .TXT makes sense exclusively for documentation, auditing, and version control of CAD standards. The biggest limitation to watch for is the complete loss of plotting functionality; the resulting text file is strictly for reading, not drafting. Convert.Guru provides a reliable, fast, and accurate way to extract this proprietary binary data into clean text, saving CAD managers the hassle of writing custom extraction scripts.