AWS CloudFormation VSCode

Overview

Language support for AWS CloudFormation templates in JSON and YAML, powered by the AWS CloudFormation Language Server.

The extension is a standalone client for the language server: it installs and updates the server, keeps it running, and adds an AWS region selector to the status bar.

Features

Editing

• Completion: resource types, properties, intrinsic functions, template sections, and references to parameters, conditions, and mappings, including inline completions while you type
• Hover documentation: contextual help for resources, properties, and functions
• Go to definition: navigate to the definition of a referenced parameter, resource, condition, or mapping
• Document symbols: template structure in the Outline view and breadcrumbs
• Code actions: quick fixes for diagnostics, extracting hardcoded values to parameters, and inserting related resources

Validation

• Syntax: immediate feedback on JSON and YAML errors
• Schema: resource schema validation using the schemas of the selected AWS region
• cfn-lint: linting with the bundled cfn-lint (no local Python installation required) or a local cfn-lint executable of your choice, with configurable delay and rule customization
• CloudFormation Guard: policy-as-code validation against managed rule packs (default: cis-aws-benchmark-level-1) or a custom rules file

File support

• A CloudFormation language mode with syntax highlighting for .template and .cfn files
• CloudFormation templates in .json, .yaml, .yml, and .txt files

Getting started

1. Install the extension (see Installation).
2. Open a CloudFormation template. The language server starts automatically and diagnostics appear in the editor and the Problems view.
3. Pick the AWS region whose resource schemas you want to validate against: click the AWS Region item in the status bar or run AWS CloudFormation: Update Region. The default is us-east-1, and the choice is remembered across sessions.

Requirements

• Visual Studio Code 1.91 or later
• Internet access on first activation: the extension downloads a verified release of the language server into the user cache directory (~/Library/Caches/aws/language-servers on macOS, %LOCALAPPDATA%\aws\language-servers on Windows, ~/.cache/aws/language-servers on Linux). Later activations reuse the cached install and fall back to it when a newer release cannot be downloaded. Regional resource schemas are downloaded on demand from the public CloudFormation schema endpoint of the selected region.

AWS account access

The extension does not currently pass AWS credentials to the language server. Everything above works without an AWS account. Server features that call AWS APIs on your behalf, such as deploying a template, listing stacks, server-side template validation, and importing resource state, are not available in this extension.

Commands

Command	Description
AWS CloudFormation: Update Region	Select the AWS region whose resource schemas are used
AWS CloudFormation: Restart LSP	Restart the language server

Settings

Setting	Default	Description
aws.cloudformation.hover.enabled	true	Enable hover documentation
aws.cloudformation.completion.enabled	true	Enable completion
aws.cloudformation.diagnostics.cfnLint.enabled	true	Enable cfn-lint diagnostics
aws.cloudformation.diagnostics.cfnLint.lintOnChange	true	Run cfn-lint when the document changes
aws.cloudformation.diagnostics.cfnLint.delayMs	3000	Delay before running cfn-lint after a change
aws.cloudformation.diagnostics.cfnLint.path	""	Path to a local cfn-lint executable; empty uses the bundled version
aws.cloudformation.diagnostics.cfnLint.customization	{ "includeChecks": ["I"] }	cfn-lint rule customization (ignore, include, mandatory, regions, ...)
aws.cloudformation.diagnostics.cfnGuard.enabled	true	Enable CloudFormation Guard diagnostics
aws.cloudformation.diagnostics.cfnGuard.validateOnChange	true	Run cfn-guard when the document changes
aws.cloudformation.diagnostics.cfnGuard.delayMs	1000	Delay before running cfn-guard after a change
aws.cloudformation.diagnostics.cfnGuard.enabledRulePacks	["cis-aws-benchmark-level-1"]	Managed rule packs to validate against
aws.cloudformation.diagnostics.cfnGuard.rulesFile	""	Path to a custom cfn-guard rules file; empty uses the enabled rule packs
aws.cloudformation.trace.server	"off"	Trace communication with the language server (messages, verbose)
aws.iac.telemetry.enabled	false	Share anonymous usage telemetry with AWS
aws.cloudformation.telemetry.logLevel	"info"	Log level of the extension output channel; applies after a window reload

Telemetry

Telemetry is off by default. On first activation the extension asks whether to share anonymous usage data with AWS; you can change the choice at any time with aws.iac.telemetry.enabled. The setting is specific to this extension; it does not read or change the telemetry preference of any other extension. See the language server's telemetry documentation for what is collected.

Troubleshooting

• The extension and the language server log to the AWS CloudFormation channel in the Output view. Set aws.cloudformation.telemetry.logLevel to debug for more detail, and aws.cloudformation.trace.server to messages or verbose to see the protocol traffic.
• If the server stops responding, run AWS CloudFormation: Restart LSP. A restart re-resolves the server install and repairs an incomplete one.
• To force a fresh download, delete the language-servers/cloudformation-languageserver folder under the cache directory listed in Requirements and restart the server.
• Bugs and feature requests: GitHub issues.

Installation

Install AWS CloudFormation from the Visual Studio Code Marketplace or Open VSX, or download the .vsix package from the releases page and install it with code --install-extension aws-iac-vscode.vsix or Extensions: Install from VSIX... in VS Code.

Contributing

See CONTRIBUTING.md for how to report issues and submit pull requests, including how to report security issues. This project follows the Code of Conduct.

License

Licensed under the Apache License 2.0. Third-party licenses are listed in THIRD-PARTY-LICENSES.txt.