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YAML Formatter / Validator

Tidy YAML — normalize indentation, convert tabs to spaces and flag tab-indent errors.

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YAML Formatter / Validator is free to use as often as you like, directly from this page. It sits under JSON, XML & formats in our catalogue, alongside XML Formatter / Validator and JSON formatter, minifier and validator.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What is YAML Formatter / Validator?

Tidy YAML — normalize indentation, convert tabs to spaces and flag tab-indent errors.

When would I actually use this?

Making a machine-generated blob readable, finding the character where a parse fails, and shrinking a file before it ships.

What is the most common mistake?

Assuming valid means correct. A document can parse cleanly and still have the wrong shape for whatever will read it — validation checks the syntax, not the schema.

Is there a tool for the next step?

JSON formatter, minifier and validator is the closest one after this: Format, beautify or minify JSON — with instant validation.

What else is worth having open alongside it?

SQL Formatter and UUID Validator / Decoder — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Parsing and serialisation follow each format's specification. Key order and whitespace are not semantically meaningful in JSON or YAML, so a reformatted document is equivalent even when the bytes differ.

Further reading

All guides →
ExplainerYAML Looks Friendly and BitesYAML is JSON plus a type-inference layer, and the inference is the dangerous part. The same file run through a YAML 1.2 parser and a YAML 1.1 parser: no is a string in one and false in the other, 01234 is 1234 in one and 668 in the other, and 12:30:00 is a number in one of them.ExplainerXML to JSON: Attributes, Repetition, and the Single-Element Array TrapTwo documents that differ only in how many children exist produce two different JSON shapes, and no converter can tell them apart without a schema. Plus what this one really does with attributes, mixed content and whitespace — and the one thing it still cannot record.GuideBeautify or Minify: What Each Is For, and What It Does to the WeightFour real stylesheets run through the minifier, measured raw and after gzip. Stripping every space saved 48, 103, 104 and 147 compressed bytes; stripping comments saved 57, 1 358, 2 420 and 1 042. Plus the five inputs this minifier breaks.ComparisonJSON vs XML: What's the Difference?JSON and XML both store structured data as text, but they trade off differently. Here's how each looks, where each wins, and how to choose.ExplainerWriting a Date as ISO 8601, and Why It Is the Only Unambiguous Format01/02/2026 is 1 February in most of Europe and 2 January in the United States, and nothing in the string says which. ISO 8601 fixes that, sorts as text, and stops being ISO 8601 in four specific places that RFC 3339 rejects.How-toHow to Convert JSON to CSV: Flattening Arrays of Objects into Rows and ColumnsA practical guide to turning a JSON array of objects into a clean CSV file, including how to flatten nested fields and handle the tricky edge cases.