JSON Formatter

What each button actually does

All three buttons parse the input with the browser's JSON.parse and write it back out with JSON.stringify. The two Format buttons pass an indent of two or four spaces; Minify passes no indent, which removes every line break and every space outside string values. Spaces inside strings are kept, so the sample's All Day Toolkit stays intact.

On the sample object the three outputs are 75 characters minified, 105 characters with two-space indentation and 123 with four. Formatting also normalises the layout: one property per line, arrays expanded one element per line, and a single space after each colon. There is no option to keep short arrays on one line or to sort keys.

Reading the error message

The text in the red box comes straight from the browser, so the wording differs between Chrome, Firefox and Safari, but every browser reports a position. In Chrome the position is a zero-based character offset, followed in recent versions by a line and column. Count from the start of your text, or paste it into an editor that shows column numbers, to land on the exact spot.

Things the round trip changes silently

• Integers above 2^53 lose precision: an id of 12345678901234567890 comes back as 12345678901234567000. Do not reformat files containing 64-bit identifiers such as Twitter or Discord snowflakes.
• Numbers are normalised: 1.0 becomes 1 and 1e3 becomes 1000.
• Duplicate keys collapse to the last one. {‘a’:1,‘a’:2} formats as a single a with the value 2.
• Keys that look like whole numbers are moved to the front in ascending order, so an object with keys b, a, 10, 2 is written out as 2, 10, b, a. All other keys keep their original order.
• Escapes are resolved: \u00e9 becomes é and \/ becomes a plain slash.

What counts as valid here

The parser follows RFC 8259 strictly. Comments, trailing commas, single quotes, unquoted keys, hexadecimal numbers, NaN, Infinity and undefined are all rejected. Files in the looser JSONC or JSON5 dialects, including tsconfig.json and VS Code settings with comments, will fail until the comments and trailing commas are removed. On the other hand, any JSON value is accepted at the top level, so a bare number, a string in quotes or an array formats fine.

Everyday uses

• Reading an API response copied from curl or a browser's network tab, where everything arrived on one line.
• Checking a webhook payload or a config file for a stray comma before deploying.
• Minifying a JSON blob before pasting it into an environment variable, a data attribute or a command-line flag.
• Comparing two responses: format both with the same indent, then diff them in your editor.

What the formatter leaves out

There is no collapsible tree view, syntax colouring, key sorting or schema validation; the output is a plain read-only text box. Multi-megabyte payloads parse fine, but scrolling a very large text box can be slow, so for files of that size an editor is a better fit.