JSON Beautifier and Validator
A free, in-browser tool for developers, API testers, and data analysts. Paste minified or malformed JSON and get clean, indented, validated output instantly — with live updates as you type. The same tool handles XML, SQL, and HTML when you need it.
Open the JSON BeautifierWhat it does
The JSON beautifier takes a string of JSON, parses it with the same rules a strict JSON consumer would apply, and re-emits it with consistent indentation, predictable key ordering (optional), and clear error reporting if the input is invalid. It is the kind of tool you reach for thirty times a day when you live inside API payloads, log lines, or configuration files.
The validator part is just as important. JSON looks deceptively simple, but real-world JSON arrives from many sources — handwritten config, generated payloads, copy-pasted curl output, log dumps that have been re-escaped twice — and a tool that simply pretty-prints the parts it can parse is not enough. This tool tells you exactly where the input stopped being valid JSON and why, with a line and column for the failing character.
Because the same workflow applies to other text formats, the tool also handles XML (indented elements, self-closed empty tags), SQL (canonical keyword case, clause-per-line formatting), and HTML (tag-pair indentation with attribute wrapping). It auto-detects which format you pasted, so you do not have to choose.
Who it's for
- Developers reading API responses in a terminal or a Postman pane that has no built-in beautifier. The keyboard-fast workflow — paste, glance, copy — is faster than wiring up a CLI tool.
- API testers and QA engineers diffing two responses or hunting for a malformed field in a payload that the server is rejecting.
- Data analysts and BI engineers who get a column of stringified JSON in a database query and need to make sense of it before writing the next query.
- Site reliability and ops staring at log lines that contain pretty-printable structured data — usually JSON, sometimes XML — buried inside a textual log envelope.
- Technical writers and educators preparing examples for documentation, where indentation and key ordering matter for readability.
When to use it
- Debugging API responses. Minified JSON from a production endpoint becomes legible in one paste.
- Cleaning up minified JSON. Pull a single-line response out of a log, expand it, and read it like a normal nested document.
- Validating before commit. Quick sanity check on a hand-edited
package.json,tsconfig.json, or any other config file before you commit a typo. - Comparing structures. Beautify two payloads with sorted keys, then paste them into the diff tool for a clean side-by-side.
- Composing test fixtures. Build up an OpenRTB bid request or a webhook payload by hand and have the validator catch missing commas as you go.
Features
| Feature | What it does |
|---|---|
| Auto-detect format | Sniffs the first non-whitespace character and the overall shape to pick JSON, XML, SQL, or HTML — no manual mode switch needed. |
| Configurable indent | 2 spaces, 4 spaces, or tab. Persisted between sessions in local storage. |
| Sort keys | Optional. Sorts object keys alphabetically at every depth — useful when you want to diff two payloads structurally. |
| Live mode | Reformats as you type or paste. Off by default for very large inputs. |
| Error position highlighting | When parsing fails, the editor scrolls to and highlights the exact character that broke the input, with a short explanation. |
| Minify mode | The reverse of beautify. Strip all whitespace and produce a compact one-line representation. |
How it works
Everything happens in the browser. The page loads a small JavaScript bundle that implements a tolerant recursive-descent parser for JSON, a lightweight tokenizer for XML and SQL, and a simple tree-builder for HTML. When you paste input, the tool parses it, builds an in-memory representation, and serializes that representation back out using your chosen indent and key-order rules.
Nothing is uploaded. There is no fetch to a backend, no telemetry that captures the payload, no third-party service in the loop. You can open the network panel in DevTools, paste any sensitive payload, and confirm that the only network activity is the static asset load for the page itself.
Why client-side matters for JSON. Many "online JSON formatters" upload your input to a backend. For most personal projects that is fine, but if your JSON contains an internal token, a bid response with deal IDs, or a customer payload, a client-side tool is the only safe option.
Common pitfalls in JSON
Three classes of mistakes account for almost every JSON error you will hit in the wild.
Trailing commas
JavaScript object literals allow a trailing comma after the last element. Strict JSON does not. A payload like {"a":1,"b":2,} will fail. Many editors silently leave a trailing comma behind when you delete the last property; the validator catches them with a clear line/column.
Unquoted keys
Again, JavaScript object literals tolerate this. JSON does not. {name:"Alice"} must be {"name":"Alice"}. Tools that auto-generate JSON from JS templates sometimes leak unquoted keys.
Control characters in strings
Literal newlines, tabs, or bell characters inside a JSON string value must be escaped (\n, \t, ). When you paste JSON that includes a multi-line free-text field straight out of a database, you frequently see this error. The position highlighter points to the offending raw character so you can spot it.
Comments
JSON does not have comments. // like this or /* like this */ will fail to parse. Some flavors (JSON5, JSONC) do allow comments — see the FAQ for how to handle those.
Single vs double quotes
JSON strings must use double quotes. {'key':'value'} is not valid JSON. Copy-pasted snippets from JavaScript or Python source code often hit this.
Frequently asked questions
Is large JSON OK?
Yes, up to the limits of your browser's memory. The parser streams through the input rather than building intermediate string copies, and modern browsers handle tens of megabytes of JSON without trouble. For hundred-megabyte log dumps, the tool will still work but live mode will lag — turn it off and reformat manually with a button press instead.
Does it modify my data?
The output is semantically identical to the input. Whitespace is normalized, optionally keys are sorted, and that is it. Numbers are preserved in their original textual form so very large integers (which exceed JavaScript's safe-integer range) round-trip without loss of precision in the output text.
Can it handle JSON5?
JSON5 is a superset that allows comments, trailing commas, single-quoted strings, and unquoted keys. The default mode is strict JSON, but you can enable a tolerant parser that accepts JSON5 input. The output is still strict JSON, so you can use the tool as a JSON5-to-JSON converter.
What about JSONP?
JSONP is JSON wrapped in a function call: callback({"a":1}). If you paste a JSONP response the strict parser will fail at the opening identifier. Enable JSONP mode and the tool strips the wrapper before parsing, then re-emits just the payload.
Does it preserve key order?
By default yes — JSON does not formally guarantee key order, but most parsers (including the one used here) preserve insertion order, and the output respects it. Enable the sort-keys option to override that and produce a canonical, alphabetical key order at every depth.
Can I convert JSON to CSV here?
Not in this tool — use the JSON to CSV converter for that. The beautifier is focused on parsing, validating, and formatting; tabular flattening is a different problem with its own choices to make.
How it compares to CLI tools
| Tool | Strength | Where this tool wins |
|---|---|---|
jq |
Best-in-class JSON querying and transformation. Indispensable in pipelines. | For a one-shot "what does this payload look like?" inspection, opening a browser tab and pasting is faster than typing jq . and copying input via a shell. |
jsonlint |
Strict parser with clear error messages. Great for scripted validation. | The browser tool shows the error inline at the failing character, with surrounding context, instead of just printing a line number. |
python -m json.tool |
Already installed on every developer laptop. | Live mode and key sorting without re-running the command. Plus it does XML, SQL, and HTML in the same place. |
| IDE built-in formatters | Convenient when the JSON is already in a file you have open. | For inspecting transient payloads — a curl response, a clipboard snippet, a webhook body — you do not have to create a file first. |
Tip. Combine tools. Beautify here, then diff in the diff tool, then escape strings for embedding in code in the escape/unescape tool. Each tool does one thing, and they compose cleanly.
Related tools
- Online Diff Tool — compare two beautified JSON payloads side-by-side
- JSON to CSV converter — flatten JSON arrays into spreadsheet rows
- Escape and unescape — embed JSON inside other JSON, code, or URLs