YAML to JSON Converter

Why YAML Took Over Config Files, and the Price It Paid

JSON is dense with quotes and braces, and you can't add comments. Configuration files are meant to be opened and modified by humans every day, who need to leave notes like "why did I set this value this way?" JSON fails at both. That's why Docker Compose, Kubernetes, GitHub Actions, and Ansible all went with YAML.

But this comes at a price: structure is defined by indentation. One misplaced space can change the meaning of the entire file, and it's invisible in an editor. This tool's value lies in showing you how a "pretty-looking YAML" file is actually interpreted by converting it to JSON. When in doubt, convert it to JSON to check if the nesting matches what you intended.

The Norway Problem: When 'NO' Accidentally Becomes `false`

In YAML 1.1, `yes`/`no`/`on`/`off`/`y`/`n` were also booleans. This led to the famous "Norway problem," where listing the country code for Norway (`NO`) would be parsed not as the string "NO" but as the boolean value `false`. For example, `countries: [KR, JP, NO]` would become `[KR, JP, false]`.

YAML 1.2 removed these, recognizing only `true`/`false` as booleans. This tool follows the 1.2 standard, so `NO` is correctly parsed as the string "NO". But here's a more important fact: this tool's result might differ from how your actual server interprets the file.

How to Quickly Catch Tab and Indentation Errors

YAML does not allow tabs for indentation. This tool will find any line containing a tab and point out its line and column number. The real problem is when you don't remember adding a tab. This usually happens when you copy-paste from another document or your editor is configured to insert tab characters for the Tab key.

• In VS Code, click the "Spaces: 2" indicator in the bottom-right corner and change it to "Indent Using Spaces". Adding `[*.yml]` and `indent_style = space` to your `.editorconfig` file will keep your whole team safe.
• If you can't see the error's cause on the line indicated, check the line directly above it. It's common for an error on one line (like an unclosed bracket or a missing space after a colon) to be caught on the next line.
• A key-value pair must have a space after the colon (e.g., `key: value`). Without the space, `key:value` is not a valid mapping.
• If a value needs to contain a colon followed by a space (e.g., timestamps, URL descriptions), you must wrap it in quotes. The "Insert Example" data includes an example of this.

Anchors (&) and Aliases (*) Are Not Supported

YAML has anchor/alias syntax and merge keys (`<<`) for defining a value once and reusing it. You'll often see this in the `x-common` pattern in `docker-compose.yml` or GitLab CI configurations. This parser does not implement this syntax. Instead of silently producing an incorrect result, it will halt with an error pointing to the line number.

We decided that failing silently is more dangerous. Ignoring an anchor results in a JSON where the referenced block is completely missing. It might look correct at a glance, leading to an error that's only discovered after deployment.

# This kind of file will cause an error
x-base: &base
  restart: always
  logging:
    driver: json-file

services:
  api:
    <<: *base        # Merge key and alias
    image: myapi:1.0

# It will be converted if you expand it like this
services:
  api:
    restart: always
    logging:
      driver: json-file
    image: myapi:1.0

Converting from JSON to YAML

The reverse direction is also common in practice. You might need to turn a JSON config from an API response into a draft YAML manifest, or you might need to dump a config object created in code into a file.

This tool adds quotes only when a string could be misinterpreted as another type. This includes values that look like numbers ("123"), booleans ("true"), or null; values containing a colon or `#`; values with leading or trailing whitespace; and the empty string. Long strings with newlines are converted to block scalars (`|`) for better readability.

Checking the "Short arrays on one line" option will render short arrays in flow style, like `[8080, 8443]`. This can dramatically reduce the line count in files with many short arrays, such as port lists or tags. On the other hand, if you plan to add a comment to each item, it's better to leave this option off.

The "↔ Result to Input" button is useful for round-trip validation. By converting YAML → JSON → back to YAML and comparing it with the original, you can visually confirm that the parser's interpretation of the structure matches your own.