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.ATC file extension

To open .ATC files on Windows, if the file came from an ACUCOBOL-GT Thin Client system, install or use the Micro Focus ACUCOBOL-GT Thin Client environment and open the .ATC file with acuthin.exe.

To open a .ATC file, first identify whether it belongs to Micro Focus ACUCOBOL-GT Thin Client or Autodesk AutoCAD tool palettes. On Windows, ACUCOBOL-GT .ATC files are associated with acuthin.exe, while AutoCAD Tool Catalog .ATC files are opened or referenced by Autodesk AutoCAD products.

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Last updated: April 29, 2026 · Reviewed by Julian Stricker

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .ATC files

Use these platform-specific instructions to open .ATC files safely.

Windows

  1. If the file came from an ACUCOBOL-GT Thin Client system, install or use the Micro Focus ACUCOBOL-GT Thin Client environment and open the .ATC file with acuthin.exe.
  2. If the file came from an AutoCAD workflow, open or reference it in Autodesk AutoCAD or AutoCAD Civil 3D as a Tool Catalog file.
  3. If you are unsure which type it is, open a copy in a plain-text editor first; AutoCAD Tool Catalog files are XML-like, while ACUCOBOL-GT files contain Thin Client launch parameters.
  4. Do not rename the file extension to force another program to open it.
Full Windows guide

Mac

  1. There is no confirmed native macOS handler in the provided sources for ACUCOBOL-GT .ATC command-line files.
  2. If the file appears to be XML tool data, inspect a copy with a text editor or use an Autodesk AutoCAD environment that supports the catalog you received.
  3. If it belongs to an ACUCOBOL-GT deployment, transfer it to the intended Windows Thin Client environment or ask the sender for the required client software.
Full Mac guide

Linux

  1. Linux media-type databases may recognize .atc as application/vnd.acucorp, but that recognition does not mean an opener is installed.
  2. Inspect a copy with a text editor to determine whether it contains ACUCOBOL-GT launch parameters or AutoCAD XML tool data.
  3. Use the original application environment, or transfer the file to a Windows system with the required Micro Focus or Autodesk software.
Full Linux guide

iOS

  1. iOS does not have a common native opener for .ATC files.
  2. Use Files to preview the file only if it is plain text or XML, or transfer it to the desktop system and application that created it.
Full iOS guide

Android

  1. Android does not have a common native opener for .ATC files.
  2. If you only need to identify the file, open a copy in a trusted text editor; otherwise transfer it to the intended Windows desktop application.
Full Android guide

Security notes

  • ACUCOBOL-GT .ATC files can contain launch parameters for a Thin Client session; review files from untrusted sources before opening because they may cause the client to connect to an unexpected host or application.
  • AutoCAD .ATC files contain XML tool data; inspect untrusted catalogs before importing because they can add tools or references to your CAD environment.
  • Do not use a browser or file manager prompt to automatically open .ATC files from unknown websites; save and verify the source first.
  • Because Apache Tika recognizes .ATC by filename pattern with no magic signature, do not rely on the extension alone to prove the file type.

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Can't open this file?

These are the most common causes and fixes when .ATC files fail to open.

Common reasons

  • The wrong program opens the .ATC file
  • ACUCOBOL-GT .ATC file does not launch
  • Web-launched .ATC file downloads instead of opening
  • AutoCAD does not show the expected tools

Fix steps

  1. Confirm the source of the file: ACUCOBOL-GT Thin Client deployment or AutoCAD tool palette/catalog workflow.
  2. Open a copy in a text editor to look for XML tool catalog data or Thin Client command-line parameters.
  3. Change the Open With association only after you know which application created the file.

OS-specific troubleshooting

What is a .ATC file?

.ATC files registered under the MIME type application/vnd.acucorp are ACUCOBOL-GT Thin Client command-line files; they store parameters used to launch Thin Client applications. Another documented use is Autodesk AutoCAD Tool Catalog files, which contain XML tool data for tool palettes. The extension alone is not enough to identify the file reliably, because some tools recognize .atc by filename pattern only and not by a unique magic signature.

Background

In the ACUCOBOL-GT Thin Client workflow, .atc and .acutc files define command-line parameters for acuthin.exe. Micro Focus documentation describes these files as a way to launch Thin Client applications, including from a web page when served with the appropriate Thin Client MIME content type.

Common MIME types: application/vnd.acucorp

Further reading

Authoritative resources for more details on the .ATC format.

Common .ATC issues

The wrong program opens the .ATC file

The .ATC extension is used by more than one documented format, so file associations can be misleading.

  1. Confirm the source of the file: ACUCOBOL-GT Thin Client deployment or AutoCAD tool palette/catalog workflow.
  2. Open a copy in a text editor to look for XML tool catalog data or Thin Client command-line parameters.
  3. Change the Open With association only after you know which application created the file.

ACUCOBOL-GT .ATC file does not launch

The Thin Client may not be installed, the file may not be associated with acuthin.exe, or the command-line parameters may not match the target deployment.

  1. Install or update the Micro Focus ACUCOBOL-GT Thin Client software required by the organization that provided the file.
  2. Associate .ATC or .ACUTC files with acuthin.exe if your deployment expects double-click launching.
  3. Ask the administrator or sender to verify the server, path, and parameter values in the .ATC file.

Web-launched .ATC file downloads instead of opening

For Thin Client web launching, the server must send the file with the expected Thin Client MIME content type and the client machine must have a handler installed.

  1. Confirm that the workstation has the required Thin Client software installed.
  2. Ask the website administrator to verify the MIME/content-type configuration for .ATC or .ACUTC files.
  3. Save the file and open it manually with the intended Thin Client application if permitted by your organization.

AutoCAD does not show the expected tools

An AutoCAD .ATC Tool Catalog file may reference tool data, paths, or resources that are not available on your computer.

  1. Open the file in the AutoCAD environment that matches the project or organization that supplied it.
  2. Check whether referenced tool palettes, blocks, support files, or network paths are available.
  3. Ask the sender to provide the complete tool catalog package, not just the .ATC file, if items are missing.

FAQ

What program opens a .ATC file?

For ACUCOBOL-GT Thin Client files, use the Micro Focus Thin Client application associated with acuthin.exe. For AutoCAD Tool Catalog files, use Autodesk AutoCAD or AutoCAD Civil 3D.

Is .ATC the same as .ACUTC?

For the ACUCOBOL-GT Thin Client use case, both .atc and .acutc are documented as command-line file extensions and are mapped to application/vnd.acucorp.

Can I convert a .ATC file by renaming it?

No. Renaming only changes the filename suffix. Use the application that created the file, or export/import through that application if it provides a supported conversion path.

Why does my .ATC file look like text or XML?

Some .ATC files are configuration-style files rather than documents. AutoCAD Tool Catalog .ATC files contain XML tool data, and ACUCOBOL-GT .ATC files contain launch parameters.

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