What Is .psd1

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Last updated: April 11, 2026

Quick Answer: .psd1 is a PowerShell module manifest file that contains metadata about PowerShell modules, including version, author, description, and dependencies. First introduced with PowerShell 2.0 in 2009, .psd1 files are essential for publishing modules to the PowerShell Gallery and managing module configuration.

Key Facts

.psd1 files are required manifests for publishing to PowerShell Gallery, which hosts over 10,000 modules as of 2024
The file format uses PowerShell hash table syntax and is a plain text file editable in any text editor
PowerShell 2.0 introduced .psd1 manifest files on October 12, 2009, revolutionizing module distribution
.psd1 supports advanced features including version constraints, required modules, and PowerShell version compatibility checks
Each .psd1 file typically contains 15-30 key properties defining module behavior, dependencies, and metadata

Overview

A .psd1 file is a PowerShell module manifest file that serves as a configuration blueprint for PowerShell modules. It contains structured metadata in PowerShell hash table format, describing everything from the module's version and author to its dependencies and available functions. These files are plain text documents that can be edited in any text editor, making them accessible to developers of all skill levels.

Introduced as part of PowerShell 2.0 in October 2009, .psd1 manifests became the standard way to package and distribute PowerShell modules. The format has since become essential infrastructure for the PowerShell ecosystem, with over 10,000 modules published to the official PowerShell Gallery relying on properly configured .psd1 files. Organizations worldwide use .psd1 manifests to manage internal module distribution, version control, and dependency management.

How It Works

A .psd1 manifest file operates as a structured declaration of module properties, enabling PowerShell to automatically load and manage modules according to specified requirements. The file uses hash table syntax native to PowerShell, making it both human-readable and machine-parseable. When PowerShell loads a module, it reads the .psd1 manifest to determine available commands, version requirements, and any prerequisite modules.

Module Metadata: The .psd1 file declares core information including ModuleVersion, Author, CompanyName, Description, and Copyright, providing essential documentation about the module's origin and purpose.
Function and Cmdlet Declaration: The FunctionsToExport and CmdletsToExport properties specify which functions and cmdlets the module makes available to users, controlling the public interface while allowing private helper functions to remain hidden.
Dependency Management: The RequiredModules property lists prerequisite modules that must be installed before the module functions correctly, ensuring all necessary dependencies are available at load time.
Version Constraints: The PowerShellVersion property specifies minimum PowerShell version requirements, while RequiredAssemblies defines .NET assemblies the module depends on, preventing compatibility issues.
Nested Module Organization: The NestedModules property enables complex module structures where primary modules can load secondary modules, supporting sophisticated modular architecture patterns.

Key Comparisons

Aspect	.psd1 Manifest File	.psm1 Module Script	JSON Configuration
Purpose	Declares module metadata and configuration	Contains actual PowerShell code and functions	Stores application-level data only
Format	PowerShell hash table syntax	PowerShell scripting language	JSON key-value pairs
Executed by	PowerShell module loader automatically	Explicitly imported by Import-Module	Application-specific parsing
Contains Code	No, metadata and declarations only	Yes, executable PowerShell functions	No, data structure only
Required	Yes, for Gallery publication	Yes, contains module logic	Optional, application-dependent

Why It Matters

.psd1 manifest files form the foundation of PowerShell's module ecosystem, enabling standardized distribution, version management, and dependency tracking across thousands of published modules. Without properly configured manifests, modules cannot be published to the official PowerShell Gallery, limiting their discoverability and adoption. Organizations depend on .psd1 files to enforce version compatibility, prevent broken dependencies, and maintain control over which module versions are deployed in production environments.

Ecosystem Standardization: The .psd1 format creates a universal standard that PowerShell Gallery and all compatible package managers understand, enabling seamless module discovery and installation across organizations and the global community.
Version Control and Compatibility: Manifests enable sophisticated version management where specific versions of dependent modules can be required, preventing breaking changes and ensuring reproducible module deployments across development, testing, and production environments.
Security and Auditing: .psd1 files document module authors, versions, and dependencies, creating an auditable record of module metadata essential for compliance, security reviews, and understanding the provenance of installed modules.
Automated Dependency Resolution: PowerShell tooling automatically parses .psd1 manifests to resolve module dependencies, automatically downloading and installing required prerequisite modules without manual intervention.

The .psd1 format represents a critical standardization point in PowerShell infrastructure. By providing a consistent, machine-readable declaration of module properties and requirements, manifests enable the sophisticated tooling, dependency management, and ecosystem coordination that makes PowerShell modules as reliable and manageable as components in modern software ecosystems. Whether managing internal organizational modules or contributing to the public PowerShell Gallery, developers depend on properly structured .psd1 files to communicate module requirements, maintain compatibility, and ensure reliable deployments.