What is the ATC file format?
An .atc file is a settings file used by AutoCAD's Content Browser. Rather than storing general application preferences, ATC files hold a catalog of reusable tools and palette items - such as blocks, hatch patterns and commands - that AutoCAD can publish and browse across projects and workspaces.
ATC files are XML documents and are automatically created or updated when new content such as palette items is added to the Content Browser. Each entry in the catalog references its content by a GUID and file path, so the same catalog can be shared across different user accounts or workspaces on a network without redistributing the underlying drawing files.
ATC catalogs can be used to synchronize tool sets across different user accounts or workspaces. A catalog opened in one AutoCAD installation can be published for team members to subscribe to, ensuring everyone works with the same standardized blocks and commands. Settings and tool references can also be exported to .cuix workspace files for broader configuration sharing.
Because .atc is an XML format, it can be inspected or lightly edited in any XML-capable text editor such as Notepad++. Note that the .atc extension is shared by other applications, so confirm the file contains AutoCAD XML catalog content before assuming its origin.
ATC files are used by AutoCAD and its verticals such as Civil 3D.
Security & safety
RISK: LOWAn AutoCAD .atc is XML configuration data and is not executable, so opening it to read is harmless. The only caution is that a catalog can reference external content (drawings/blocks) by path, so a shared .atc from an untrusted source could point at unexpected files - but it carries no code. Be sure you've correctly identified the .atc (it is an overloaded extension) before acting on it.
Format details
in a nutshell- ArchiCAD Template / archive content - Graphisoft ArchiCAD has used .atc-style files for template/library content; unrelated to AutoCAD's tool catalog.
- Microsoft Access data/related file - Some Access-related tooling and add-ins produced .atc files; distinct from the AutoCAD catalog format.
- Audials / media chapter file (Audials Tunebite ATC) - A few media tools used .atc for chapter/track metadata; rare and unrelated to CAD.
Programs that open ATC files
Windows4 apps
AutoCAD Civil 3D
Paid Same Content Browser workflow as AutoCAD; loads the .atc tool catalog for Civil 3D content. 
AutoCAD LT
Paid Has limited Tool Palette support; can use catalog-shared tools but with fewer Content Browser capabilities than full AutoCAD. 
AutoCAD (Content Browser)
Paid Open AutoCAD, launch the Content Browser, and load/publish the catalog there - AutoCAD consumes the .atc to populate Tool Palettes (don't open it as a drawing).
Notepad++ / any XML editor
Open-source Open the .atc as text to read or edit its XML catalog entries (useful for fixing broken references). Technical details
deep spec| File format | XML (UTF-8 text, begins with standard <?xml declaration) |
| Encoding | UTF-8 |
| Typical file size | 1 KB - 200 KB |
| Catalog content | References to reusable tools: blocks, hatch patterns, commands and palette items |
| Entry identification | Each catalog entry uses a GUID and file path to reference its drawing content |
| Schema owner | Autodesk Content Browser (AcCb) component; schema tracks the AutoCAD release |
| Folder structure | Catalog files (.atc) can be stored on a network share and subscribed to by multiple AutoCAD users |
| Associated applications | AutoCAD, AutoCAD Civil 3D and other AutoCAD vertical products |
| Operating system | Windows only (AutoCAD's Content Browser is Windows-exclusive) |
| Extension conflict | The .atc extension is also used by ArchiCAD and some Microsoft Access contexts; confirm by XML/catalog content |
| Released | AutoCAD 2004-era (with the DesignCenter Online / Tool Palettes & Content Browser) |
| Latest version | Tracks the AutoCAD release; catalog schema is stable and consumed by the Content Browser (AcCb) |
| Specification | www.autodesk.com |
ATC conversions
Community Q&A
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