What is the ADM file format?
.adm files are Administrative Template files used by Windows Group Policy to define configurable policy settings that apply to Windows machines and users. Each file describes a set of registry-backed settings, mapping them to a hierarchical UI in the Group Policy Object Editor (gpedit.msc).
The format uses a proprietary INI-like plain-text syntax organized into CATEGORY, POLICY, and KEYNAME blocks. Each POLICY entry specifies a Windows registry path and value, a typed UI control (DROPDOWNLIST, CHECKBOX, EDITTEXT, etc.), and optional explanatory text displayed in the editor. Files use ANSI/Windows-1252 encoding rather than UTF-8 and typically begin with the keyword CLASS MACHINE or CLASS USER.
.adm files were introduced with Windows 2000 and were the standard Group Policy template format through Windows XP and Server 2003. Windows Vista (2007) replaced them with .admx files (XML format) paired with .adml language-string files, which are stored centrally on the domain controller rather than duplicated inside every GPO.
Windows 10 and Windows 11 ship no .adm files; all built-in templates are ADMX/ADML. Group Policy tools on Vista and later still load custom .adm files for backward compatibility, but generate a warning and inflate SYSVOL storage because each GPO stores its own copy. Microsoft's free ADMX Migrator tool can convert legacy .adm templates to the current format.
Security & safety
RISK: LOWPlain text file defining registry paths. Cannot execute code on its own. Risk: a malicious .adm could direct Group Policy to write harmful registry values - applies only when an admin imports it into an active GPO. Do not import .adm templates from untrusted sources.
Format details
in a nutshell- MultiModule Screensaver File - Some screensaver creation tools from the 1990s-2000s used .adm for module definition files; this usage is extremely rare and the software is long discontinued.
- Generic 'admin' or 'admins' configuration file - Various legacy software used .adm as a generic admin configuration file extension; no single format standard.
Programs that open ADM files
Windows3 apps
Group Policy Object Editor (gpedit.msc)
Built-in In gpedit.msc: right-click Administrative Templates > Add/Remove Templates, add the .adm file. Windows Vista+ warns about legacy format.
Group Policy Management Console (GPMC)
Built-in Available on Windows Server / via RSAT. Load .adm templates through linked GPO settings.
Notepad (text view)
Built-in Open directly in Notepad to read or edit the policy definitions as plain text. Technical details
deep spec| Format type | INI-like plain-text Group Policy template |
| Encoding | ANSI/Windows-1252 (not UTF-8) |
| Container | Plain text (no binary wrapper) |
| Structure | Hierarchical `CATEGORY` / `POLICY` / `KEYNAME` blocks with typed UI controls |
| Registry integration | Each `POLICY` maps directly to a Windows registry key and value |
| UI control types | `DROPDOWNLIST`, `CHECKBOX`, `EDITTEXT`, `LISTBOX`, `NUMERIC` |
| Typical file size | 5 KB - 2 MB (Microsoft's base ADM templates were ~1 MB each) |
| Associated OS | Windows 2000, XP, Server 2003; legacy mode in Vista and later |
| GPO storage impact | Each GPO stores its own copy in SYSVOL, causing storage overhead vs. ADMX central store |
| Superseded by | ADMX + ADML (XML-based pair), introduced with Windows Vista (2007) |
| Released | Windows 2000 (2000) |
| Latest version | Last shipped with Windows XP / Server 2003; superseded by ADMX in Windows Vista (2007) |
| Specification | learn.microsoft.com |
ADM conversions
Community Q&A
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