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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: June 11, 2026 · Reviewed by Julian Stricker

What “reviewed” means on this page
  • Format fit: whether the “what is this file?” description matches common real-world use of the extension, including category, typical MIME types, and aliases.
  • Opening paths: whether Windows / macOS / Linux steps read plausibly for current OS dialogs and default apps; we remove fantasy menus and unsafe shortcuts.
  • Security framing: whether risk notes match the extension class (for example executables vs plain data) and whether affiliate wording does not contradict the security section.
  • Sources and further reading: whether external links point to vendors, standards bodies, or other primary references where possible; we avoid inventing details we cannot ground.
  • Limits: this is clarity and safety-messaging QA, not a guarantee that every statement is exhaustive or that every binary you download is harmless.

Full methodology in the Imprint — The Imprint also states where AI is used and what that does—and does not—replace.

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.

If you did not expect this file

This extension is usually plain data, text, or structured content—not a program by itself. The practical risk is social engineering (a scam attachment or misleading filename). For trusted senders you rarely need heavy-handed antivirus wording; use these tools when you want an extra check on unexpected downloads.

Avast

Avast offers free and premium antivirus software that protects against viruses, malware, ransomware, and phishing. Scan files before opening them to ensure safety.

Norton

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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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