Terraform Validator

Terraform Validator: Check Terraform and HCL Online

Paste Terraform configuration into this online validator to run a quick static check before using the Terraform CLI. The tool checks common structural problems such as unmatched braces and quotes, reviews Terraform block labels, and reports selected maintainability or security warnings, including missing version constraints, undocumented variables, sensitive-looking defaults, hardcoded identifiers and missing tags on common resources.

Important: This browser-based checker is a fast pre-check, not the official terraform validate command. It does not install providers or modules, load an entire working directory, contact provider APIs, inspect remote state, or guarantee that terraform plan will succeed.

How to Validate Terraform Code Online

1. Copy the Terraform or HCL configuration you want to review.
2. Paste it into the validator editor.
3. Select Validate to run the available checks.
4. Review errors first, followed by warnings and recommendations.
5. Correct the reported lines and validate the code again.
6. Run the official Terraform CLI validation in the complete project directory before planning or applying changes.

What Does terraform validate Do?

The official terraform validate command checks the configuration files in a directory for syntax validity and internal consistency. It can detect problems such as invalid argument names, incorrect value types and inconsistent module configuration after the required providers and modules are installed. It does not validate remote services, provider APIs or remote state.

Validation is useful as a local development check, editor integration or CI step. For validation in the context of real input values, a selected workspace and existing state, use terraform plan, which includes an implied validation check.

How to Validate Terraform Locally

Open a terminal in the root module directory and initialize the project before running validation:

terraform init -backend=false
      terraform validate

The -backend=false option is useful when preparing a directory for validation without accessing its configured backend. Terraform still needs referenced providers and modules to be available. For machine-readable diagnostics in automation, run:

terraform validate -json

The JSON output can contain validity status, error and warning counts, diagnostics, source ranges and code snippets. Automation should also handle failures that happen before Terraform can produce valid JSON.

What This Online Terraform Check Covers

Worked Terraform Validation Example

This configuration is structurally readable, but it contains several maintainability and security concerns:

terraform {
        required_version = ">= 1.5.0"
      }

      variable "db_password" {
        default = "example-password"
      }

      resource "aws_instance" "web" {
        ami           = "ami-0c55b159cbfafe1f0"
        instance_type = "t3.micro"
      }

The online check can warn that required_providers is missing, the variable has no description or type, a sensitive-looking value has a hardcoded default, the AMI ID is hardcoded, and the resource has no tags. A safer revision can declare the provider, define a sensitive input without a secret default, use variables for environment-specific identifiers and add appropriate tags.

Terraform Validate vs Format, Lint and Plan

Common Errors

• Unclosed block: Match every opening brace with a closing brace.
• Unclosed string: Check missing or incorrectly escaped quotation marks.
• Missing required providers: Declare provider source addresses and suitable version constraints.
• Undocumented variable: Add a meaningful description and an explicit type.
• Hardcoded secret: Never place passwords or API keys directly in a committed Terraform default.
• Online check passes but CLI fails: The CLI can detect cross-file, module and provider-schema problems that a pasted-code checker cannot.

Best Practices

• Run terraform fmt -check and terraform validate before opening a pull request.
• Pin Terraform and provider versions according to your project’s upgrade policy.
• Use variables or data sources for environment-specific IDs instead of embedding them repeatedly.
• Store secrets in an appropriate secret-management system and remember that sensitive = true mainly redacts display output.
• Run terraform plan and review the proposed changes before terraform apply.

Limitations of Browser-Based Terraform Validation

A pasted snippet cannot represent every file, module, provider plugin, variable value or state dependency in a Terraform project. This tool performs only the checks explicitly listed on this page. Always use HashiCorp Terraform or your compatible Terraform workflow for authoritative project validation, planning and deployment.

Frequently Asked Questions