YAML ↔ JSON

2. How to Convert YAML to JSON (or JSON to YAML)

Here is how to convert YAML to JSON with the tool above. The input box opens with a sample Kubernetes-style service block, so you can press Convert first and see the shape of the result.

1. Paste or drop your file. Paste text into the box, or drop a single .yaml, .yml, .json or .txt file onto the panel. The yml to json case is identical; the extension makes no difference.
2. Pick the direction. The Conversion menu offers YAML → JSON (the default) and JSON → YAML.
3. Choose the indent. Two spaces is the default; four spaces is there for projects that use it. The setting applies to either direction, so it gives you YAML to JSON pretty print output and JSON to YAML 4 space indent output from the same menu.
4. Convert, then copy or download. Press Convert. The result appears in the right-hand box with a Copy button and a Download button that saves data.json or data.yaml.

That is also how to convert JSON to YAML: switch the menu, paste the JSON, press Convert. Conversion runs when you press the button, not on every keystroke.

Inside a pipeline, a script fits better: convert YAML to JSON Python usually means a YAML library plus the json module, and a command-line YAML processor gives you a shell one-liner. Whichever you use, check which YAML version it follows: a library on the older 1.1 rules can turn NO into false where this page would not. For a one-off check, pasting it here is quicker.

3. The YAML Norway Problem, and Why NO Stays “NO”

The YAML Norway problem is the classic surprise: a list of country codes goes in, and Norway comes out as false. It happens because the older YAML 1.1 rules treated yes, no, on and off as booleans. The current YAML 1.2 specification dropped that, and this converter follows the 1.2 core rules. If you have seen YAML yes no converted to true false, here is what you get instead:

• country: NO becomes "NO" and enabled: yes becomes "yes": both stay strings. Only true and false (in any capitalisation) become booleans.
• port: 8080 becomes the number 8080, as do hex like 0x1F, floats and .inf.
• null, ~ and an empty value become null. Dates and times such as 22:30 stay strings.

The reverse direction protects the round trip: JSON to YAML quotes strings YAML would misread, such as "no", "on" or "1.0", and writes multi-line strings as literal | blocks.

4. Kubernetes, Compose, Helm, Actions and OpenAPI

Most YAML that needs converting is configuration, and each kind has one detail worth knowing.

• Convert Kubernetes YAML to JSON for kubectl patch, an API call or a script: a single manifest converts cleanly. A file with several resources separated by --- needs splitting first (see section 6).
• Docker Compose YAML to JSON: services, ports, volumes and environment blocks all convert. If the file reuses settings with <<: *defaults, that merge is not expanded.
• Helm values YAML to JSON, for --set-json or a values schema: nested maps and lists keep their types, which matters for region and feature-flag values.
• GitHub Actions workflow YAML to JSON: the on: key stays the string "on" rather than turning into true, and ${{ }} expressions are kept as text.
• OpenAPI JSON to YAML: paste a Swagger or OpenAPI spec, switch to JSON → YAML, and get the readable form with status codes such as "200" kept as quoted keys.
• Ansible YAML to JSON: playbooks and inventory convert for inspection; yes/no values stay strings, so check anything your tooling expects as a boolean.

YAML anchors and aliases to JSON work the way you would hope: define base: &b once, reference it with *b, and the JSON contains the full block in both places.

5. What Each Error Message Means and How to Fix It

Errors appear above the output box, and your input is left as it was.

• Invalid YAML near line N or Unexpected content at line N: usually a line indented to a level that does not match its siblings. Line it up with the keys it belongs beside.
• Bad flow sequence or Bad flow mapping: an inline [ ] list or { } map that was never closed, or has a stray comma.
• Unknown alias *name: a *name reference with no matching &name, often a typo.
• Invalid JSON: …: the JSON → YAML input did not parse. The detail often reads like unexpected token in JSON at position N; look there for a trailing comma, single quotes or a comment.

Two messages from other YAML tools deserve a note. Found character that cannot start any token (YAML tab) means a tab was used for indentation, which YAML forbids. This converter does not report tabs but mis-reads them, so replace indenting tabs with spaces first. The YAML error mapping values are not allowed here means a second colon on one line or a key indented under a value. Here, a line such as a: b: c does not raise an error: it becomes the string "b: c", so glance at the output and check the nesting is what you meant.

6. What It Does Not Do, With the Workaround

This converter reads a practical subset of YAML. These are the cases it does not handle, so you know before you rely on the output.

• YAML multiple documents to JSON. The --- separators are ignored, so two documents merge into one object and later duplicate keys overwrite earlier ones. Split the file and convert each document separately.
• Merge keys. <<: *base is kept as a literal "<<" key holding the anchored map. Copy the shared keys into each block if you need them flattened.
• Custom tags. CloudFormation !Ref, !GetAtt, !Sub or !!binary are not interpreted; the tag text stays inside the string value.
• Comments. Dropped going to JSON, never added going to YAML.
• Schema checks. It confirms the text parses, not that the file is valid for Kubernetes or OpenAPI.
• JSON with comments or trailing commas. JSONC and JSON5 fail with Invalid JSON. The JSON formatter helps you find the offending character.
• Tab indentation. Tabs are not reported as an error and are mis-read, so replace indenting tabs with spaces before you convert.
• Leading and trailing zeros in bare numbers. 01234 becomes 1234 and 1.10 becomes 1.1. Quote the value to keep it exactly.
• Batch or live conversion. One file or paste per press of Convert; there is no multi-file mode and no convert-as-you-type.
• Side-by-side comparison. To see what changed between two versions of a config, paste both into the diff checker.

For other formats, use the CSV to JSON converter, the XML to JSON converter and the SQL to CSV tool instead.

7. Why Cortexis Is the Best Free YAML JSON Converter

Plenty of pages offer a JSON to YAML converter online; few say which YAML rules they follow. This one is a YAML JSON converter free of sign-ups, and here is what you can check.

It sits alongside a wider set of free developer and file tools built on the same terms.

8. Frequently Asked Questions (FAQ)