Is the JSON to YAML converter free?
Yes. It is completely free to use, with no signup, no account, and no paywall.
Do I need to install anything?
No. It runs in any modern browser on desktop or mobile, with nothing to download and nothing to configure.
Does it stay local?
Yes. Your data is converted entirely in your browser and never uploaded to a server.
My string value became a boolean in YAML. Why?
This is the Norway problem, and it is a property of YAML 1.1 rather than a mistake in the conversion. YAML 1.1 treats the unquoted tokens yes, no, on, off, y, and n as booleans, so a country code of NO or a config value of off silently changes type. YAML 1.2 fixed this, but many widely used parsers still implement 1.1. The safe move is to quote any string value that could be read as a boolean, and to check the output whenever your data contains two-letter codes or on and off switches.
Do I even need to convert, given YAML is a superset of JSON?
Often not. Every valid JSON document is by definition valid YAML 1.2, so a YAML parser will happily read your JSON file as it stands. The reasons to convert are human ones: YAML is easier to read and to review in a pull request, and it supports comments. If a tool is refusing your file, check whether the problem is really the format before you convert.
Why does my leading zero disappear?
Because the value was emitted without quotes and the YAML parser read it as a number. A JSON string of "007" becomes an unquoted 007 in the output, and a parser resolves that to the integer 7, or in YAML 1.1 possibly to an octal value. The same thing happens to version strings such as "1.10", which become the float 1.1. Postcodes, product codes, and phone numbers are the usual victims. Quote them in the YAML.
Can I use tabs to indent the result?
No. Tabs are explicitly forbidden as indentation in YAML, and this is one of the most common causes of a parse error that people cannot diagnose. The output uses two spaces per level. If your editor is configured to convert leading whitespace to tabs on save, turn that off for YAML files, or the file will break in a way whose error message points at a line far from the real problem.
Is my JSON uploaded to convert it?
No. The JSON is parsed and re-emitted as YAML by JavaScript running in your browser, so nothing is transmitted. Since the JSON people convert is often a Kubernetes manifest, a CI config, or an API response with real credentials in it, that is worth knowing.