Why use a dedicated YAML validator?
YAML is whitespace-sensitive, which means a single misplaced space can break a Kubernetes deployment, a GitHub Actions workflow, or a Docker Compose file. Most editors highlight tokens but stop short of catching structural errors. This validator parses your file the same way the official YAML 1.2 spec does, so the result matches what your CI runner, deployment tool, or application library will see.
Common YAML errors this tool catches
- Inconsistent indentation - mixing tabs and spaces or unexpected indent jumps inside a list or map.
- Missing colons - forgetting the colon after a key, or putting the colon at the wrong position relative to the value.
- Unquoted special characters - colons, hashes, and angle brackets that need quoting when they appear in values.
- Duplicate keys - the same key appearing twice at the same level, which silently breaks downstream tools.
- Broken anchors and aliases - referencing an alias (
*name) before its anchor (&name), or using a name that was never declared. - Unclosed flow sequences - a stray
{or[without its closing pair.
How to read the validator output
When YAML is valid, the right pane shows a parsed JSON preview so you can verify the structure matches your intent. When it is invalid, the validator surfaces a single line-and-column pointer with a description of what the parser expected at that position. Fix that error, and the validator immediately re-checks the rest of the file.
Validating Kubernetes, GitHub Actions, and Docker Compose YAML
This tool covers the syntactic layer for any YAML file, including Kubernetes manifests, GitHub Actions workflows, Docker Compose files, Ansible playbooks, OpenAPI specs, and CircleCI configs. It does not enforce schema rules specific to those tools - kubectl apply --dry-run=client, docker compose config, and the GitHub Actions UI handle that layer. Use this validator first to confirm the file parses, then run the tool-specific checker.
FAQs
How does the YAML validator work?
Paste your YAML and the validator parses it instantly using the YAML 1.2 specification. If the syntax is valid, you see a green confirmation. If there is a problem, the validator shows the exact line and column number along with a clear error message.
What YAML errors can the validator catch?
It catches indentation errors, mismatched brackets, duplicate keys, invalid scalar types, malformed anchors and aliases, missing colons after keys, unclosed flow sequences, and other syntax problems before you ship the file.
Does it support YAML 1.2?
Yes. The validator targets the YAML 1.2 specification and supports anchors, aliases, merge keys, block scalars (literal | and folded >), tagged values, and standard scalar types including strings, numbers, booleans, and null.
Can I validate Kubernetes YAML files?
Yes. The validator confirms your Kubernetes manifest is syntactically valid YAML. It does not check Kubernetes-specific schema rules like apiVersion or kind values - use kubectl apply --dry-run for schema validation.
Is my YAML data sent to a server?
No. All YAML parsing and validation happens in your browser. Your YAML file never leaves your device, which makes the tool safe for secrets, internal config, and proprietary data.
What is the difference between a YAML linter and a validator?
A validator checks if YAML is syntactically correct and parseable. A linter goes further by enforcing style rules like indentation width, line length, and key ordering. This tool is primarily a validator with basic linting via the formatter page.
Why is my YAML file not valid?
The most common YAML errors are inconsistent indentation (mixing tabs and spaces), missing colons after keys, unquoted special characters like colons inside values, and duplicate keys at the same level. The validator points you at the exact line.
Can I validate GitHub Actions or Docker Compose YAML?
Yes for syntax. The validator confirms your workflow or compose file is parseable as YAML. For GitHub Actions schema checking, push to a branch and let the GitHub UI validate. For Docker Compose, use docker compose config.
What encoding does the validator expect?
UTF-8, the YAML 1.2 default. The validator handles standard ASCII as well as accented characters, emojis, and other Unicode. If you paste content with a BOM, the parser silently accepts it.
How large a YAML file can I validate?
Up to 5 MB per validation, which covers nearly every real-world configuration file. For larger payloads, split the file into smaller documents or run validation in your build pipeline instead.