# JSON Formatter URL: https://www.toolflux.app/en/json-formatter/ Stand: 2026-06-05 JSON formatter, validator and sorter. Type chips for every field, tree view, caret-pointed error card with common-cause list. JSON looks the same everywhere - until it breaks. The formatter below parses, formats, minifies, sorts or escapes. When something is off, it points to the spot with a caret and tells you what it expected versus what it found. ## What is JSON, and why is it so strict? JSON started in 2001 as a subset of JavaScript object literals. It became RFC 8259 (2017), the standard still in force. The strictness is by design: exactly six types, unambiguous tokenisation, no comments. Every parser ends up with the same tree. The six types are **string** (double quotes), **number** (decimal, no NaN, no Infinity), **boolean** (`true` / `false`), **null** (`null`, no `undefined`), **array** (comma-separated, order matters) and **object** (keys are strings). The type chips above show each type with its colour, sample and spec rule; the tree view colours every field the same way. Click a chip to highlight that type in the tree - useful when scanning "where are all the strings". ## How do I find the error in my JSON file? The most common pain with JSON is not "how do I format this" but "why does it break". Native `JSON.parse` throws a `SyntaxError` with position - in Chrome and Firefox as a character index into the input, which the formatter maps to line and column. The red error card above then shows: 1. **Position** - line, column, character index. 2. **Context window** - the offending line plus one above and one below, with a caret under the spot. 3. **Expected vs found** - what the parser wanted at that position and what it saw instead. 4. **Common causes** as a list: trailing comma, single quotes, unquoted key, JS comment, `undefined` or `NaN`. Safari does not always return a position; in that case the context window drops out, the message and remediation list stay visible. ## Trailing commas, single quotes and other JS heritage When pulling JSON from JS code, the same traps keep recurring: | Problem | JS accepts | JSON accepts | Fix | |---|---|---|---| | `{"a": 1,}` (trailing comma) | Yes (since ES5) | No (RFC 8259 ยง4) | Drop the comma | | `{'a': 1}` (single quotes) | Yes | No | Use double quotes | | `{a: 1}` (unquoted key) | Yes | No | Quote the key | | `// comment` | Yes | No | Strip comments | | `undefined`, `NaN`, `Infinity` | Yes | No | `null` / a real number | JSON5 reacted to these points: it allows trailing commas, single quotes, unquoted keys, comments, NaN and Infinity, but not `undefined`. JSON5 is still not the same format as JSON. If your tool or API expects strict JSON (most do), strip the JS-isms first. The error card points to the first suspect spot. ## Format, minify, sort - which when? **Format** with 2 or 4 spaces is the default for reading and code review. 2 spaces is Prettier's default and the standard in style guides like Airbnb and Google. **Minify** strips every whitespace character. Useful when JSON has to fit into an env variable, a URL query string, or a DynamoDB entry - every byte counts. **Sort keys** orders object keys alphabetically (recursive by default). Main use: comparing two similar configs without `git diff` shouting because some tool reordered keys. Arrays stay in order because position carries meaning in arrays. ## Escape and unescape - JSON inside JSON, text into JSON `Escape` turns arbitrary text into a JSON string literal. `hello "world"` becomes `"hello \"world\""`. That is `JSON.stringify(input)` under the hood - useful when embedding text into a config, hardcoding a JSON value inside a JS string, or passing free text as a JSON value to an API. `Unescape` is the reverse: a JSON string literal back to plain text. Works on a single string literal, not on a whole object - the format mode handles that. ## Frequently asked questions ### What is invalid JSON and how do I spot it? JSON is a strict subset of JavaScript. Trailing commas, single quotes, unquoted keys, comments, `undefined` and `NaN` are all forbidden. The formatter above flags the first offending position with a caret and a list of common causes. ### How do I find the error in my JSON file? On a parse error a red card appears with line, column and character position. Chrome and Firefox return the exact position; Safari often does not. ### What are trailing commas and why does JSON dislike them? A comma right before `}` or `]`. JavaScript allows it, JSON does not - RFC 8259 bans it so machine parsers can tokenise unambiguously. ### Minify or format JSON - which when? Format for reading and debugging, minify for transport or env-variable storage. One click switches. ### How do I sort keys in JSON? Switch the mode to `Sort keys` - recursive by default. Arrays stay in order. ### What is the difference between JSON and JSON5? JSON5 allows trailing commas, single quotes, unquoted keys and comments. The formatter speaks strict JSON per RFC 8259 in v1. ### What does escaping a JSON string mean? Turning arbitrary text into a JSON string literal - quotes become `\\\"`, line breaks `\\n`. `Unescape` is the reverse. ### FAQ **What is invalid JSON and how do I spot it?** JSON is a strict subset of JavaScript. Trailing commas, single quotes, unquoted keys, comments, `undefined` and `NaN` are all forbidden. The formatter above flags the first offending position with a caret and a list of common causes so you find the spot instead of hunting it. **How do I find the error in my JSON file?** Paste the JSON above. On a parse error a red card appears with line, column and character position of the first problem, plus a list of typical causes - trailing comma, single quote, JS comment. Chrome and Firefox return the exact position; Safari often does not, so the caret is hidden but the message stays. **What are trailing commas and why does JSON dislike them?** A trailing comma is a comma right before `}` or `]`. JavaScript allows it (object and array literals have since ES5), JSON does not - RFC 8259 bans it explicitly so machine parsers can tokenise unambiguously. When pulling JSON from JS code, scan list ends carefully. **Minify or format JSON - which when?** Format for reading, debugging, code review - humans need indentation. Minify for transport, env-variable stuffing, URL params, key-value stores - every whitespace byte you save adds up across files. Both modes sit side by side above; one click switches. **How do I sort keys in JSON?** Switch the mode to `Sort keys` - the formatter walks recursively and orders object keys alphabetically. Arrays stay in order because position carries semantic meaning in arrays. Untick `Sort recursively` to touch only the top level. Sorted keys make `git diff` calmer when comparing similar configs. **What is the difference between JSON and JSON5?** JSON5 is an extension that brings JS conveniences back: trailing commas, single quotes, unquoted keys, comments, hex numbers, NaN/Infinity. The formatter above speaks strict JSON per RFC 8259 in v1. If you need JSON5 (common for config files), strip the JS-isms first or wait for the V2 mode. **What does escaping a JSON string mean?** Escaping turns arbitrary text into a JSON string literal: quotes become `\"`, backslashes `\\`, line breaks `\n`. Useful when embedding text into a JSON config or hardcoding a JSON value inside a JS string. `Unescape` is the reverse: a JSON string literal back to plain text.