YAML Creator & Validator

Free YAML Creator & Validator — Write, Validate, and Format YAML Online

YAML is everywhere in modern software development. Docker Compose files, Kubernetes manifests, GitHub Actions workflows, Ansible playbooks, Helm charts, and application configuration files all use YAML as their primary format. Getting YAML right is critical — a single misplaced space or an unquoted colon can break your entire pipeline or deployment.

This free YAML creator and validator helps you write correct YAML from scratch or validate existing files before you deploy. Paste your YAML, upload a file, or load one of six built-in templates. The validator checks your YAML in real time, reporting errors with their exact line numbers and warnings for common issues like tab characters, unquoted keys with spaces, and trailing whitespace.

You can also convert valid YAML to JSON, format your YAML to remove trailing spaces and normalize blank lines, and download the result as a `.yaml` or `.json` file. Everything runs locally in your browser — your configuration files, secrets, and credentials never touch a server.

Six ready-to-use templates cover the most common YAML use cases: Docker Compose, GitHub Actions CI, Kubernetes Deployment, Ansible Playbook, application config, and a simple generic config. Each template is fully editable and serves as a starting point for your own configuration.

How to Use the YAML Validator

Four ways to get started:

1. 1

   Type or paste YAML

   Click inside the editor and start typing, or paste existing YAML. The validator checks your YAML in real time and displays errors and warnings in the right panel instantly.

2. 2

   Upload a file

   Click the Upload button to load a .yaml, .yml, .json, or .txt file from your computer. The file contents appear in the editor and are validated immediately.

3. 3

   Use a template

   Click any template button (Docker Compose, GitHub Actions, Kubernetes, etc.) to load a complete working example. Then edit it to match your needs.

4. 4

   Format and download

   Click Format to clean up trailing spaces and extra blank lines. When your YAML is valid, click Download to save a .yaml file, or use "→ JSON" to convert and download a .json file.

Why YAML Validation Matters

YAML Syntax: Common Mistakes and How to Fix Them

1. Using Tabs Instead of Spaces

This is the number one YAML error. YAML strictly requires spaces for indentation. Never use tabs, even if your editor shows them as spaces. Configure your editor to insert spaces when you press the Tab key, especially for .yaml and .yml files.

2. Inconsistent Indentation

YAML does not require a fixed number of spaces (2 or 4 are both valid), but you must be consistent within a file. Mixing 2-space and 4-space indentation in the same file causes parse errors. Stick to one convention throughout.

3. Unquoted Special Characters

Colons, hashes, brackets, and certain other characters have special meaning in YAML. If your value contains a colon followed by a space (like a URL), you must quote the value. For example: url: "https://example.com" not url: https://example.com.

4. Boolean and Null Ambiguity

YAML 1.1 (used by many parsers) interprets yes, no, on, off as booleans. Use true/false or quote these strings to be safe.

5. Missing Space After Colon

A key-value separator in YAML must be a colon followed by at least one space: key: value. Writing key:value (no space) is treated as a string, not a key-value pair.

Available Templates

Frequently Asked Questions