What is the ADML file format?
An .adml file is the language-specific resource half of a Windows Group Policy administrative template. It is always paired with a matching .admx file of the same base name: the .admx contains the policy logic and registry mappings, while the .adml holds only the localized display strings - setting names, explanatory text, and UI element labels - keyed by ID.
The format was introduced in 2007 with Windows Vista SP1 and Windows Server 2008 as part of the ADMX/ADML model that replaced monolithic .adm files. Separating logic from strings allows a single .admx to be paired with .adml files in dozens of languages without duplicating policy definitions.
.adml files are well-formed XML with a <policyDefinitionResources> root element. Inside, a <stringTable> maps string IDs to localized text, and a <presentationTable> defines how UI controls - dropdowns, checkboxes, text fields - are labelled in the Group Policy editor.
The files are deployed to a PolicyDefinitions folder - locally at C:\Windows\PolicyDefinitions\<lang>\ or in the SYSVOL Central Store at \\<domain>\SYSVOL\<domain>\Policies\PolicyDefinitions\<lang>\ - where <lang> is a BCP 47 tag such as en-US. The Group Policy Object Editor (gpedit.msc) and Group Policy Management Console load .adml files automatically at startup.
Security & safety
RISK: LOWPlain XML text file; cannot execute on its own. Malicious .adml files paired with malicious .admx files could configure unwanted Group Policy settings if placed in PolicyDefinitions by an attacker with admin access - but that already requires administrative privileges. For most users these files are safe to open and read.
Format details
in a nutshellPrograms that open ADML files
Windows4 apps
Group Policy Object Editor (gpedit.msc)
Built-in Place .admx in C:\Windows\PolicyDefinitions\ and .adml in C:\Windows\PolicyDefinitions\en-US\; then run gpedit.msc to use the policies.
Group Policy Management Console (GPMC)
Built-in Deploy ADMX/ADML to the Central Store on the domain controller SYSVOL; GPMC picks them up automatically. 
Visual Studio Code
Free Open .adml file; VS Code auto-detects XML and provides syntax highlighting and folding. Technical details
deep spec| File format | Well-formed XML; root element `<policyDefinitionResources>` |
| Character encoding | UTF-8 (Microsoft-supplied templates may use UTF-16 LE with BOM) |
| MIME type | text/xml (also application/xml) |
| Schema version | `revision="1.0" schemaVersion="1.0"` attribute in the root element |
| Required pairing | Always deployed alongside a matching `.admx` file of the same base name |
| String section | `<stringTable>` maps string IDs to localized display text for policy settings |
| Presentation section | `<presentationTable>` defines UI control labels (dropdowns, checkboxes, text fields) |
| String reference syntax | `.admx` references strings as `$(string.ID)`; `.adml` resolves them by that ID |
| Domain Central Store path | `\\<domain>\SYSVOL\<domain>\Policies\PolicyDefinitions\<lang>\` |
| Local Group Policy path | `C:\Windows\PolicyDefinitions\<lang>\` |
| Language subfolder naming | BCP 47 language tag, e.g. `en-US`, `de-DE`, `fr-FR`, `ja-JP` |
| Introduced | Windows Vista SP1 / Server 2008 (2007); replaced monolithic `.adm` templates |
| Loaded by | Group Policy Object Editor (`gpedit.msc`) and Group Policy Management Console (GPMC) |
| Released | 2007 (Windows Vista SP1 / Server 2008) |
| Latest version | No independent version; tied to Windows Group Policy platform; current templates ship with Windows 11 / Server 2025 |
| Specification | learn.microsoft.com |
Community Q&A
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