JSON & JSONL Parser / Formatter
Free online JSON & JSONL parser. Validate, pretty-print, and minify JSON with syntax highlighting. Auto-detects JSON Lines (.jsonl). 100% client-side.
Paste JSON on the left to see the formatted result hereRelated Tools
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Frequently Asked Questions
What is JSON validation?
It checks whether the JSON is written according to correct syntax. If there are errors such as missing quotes, incorrect commas, or mismatched brackets, the error location and cause are shown.
Can I change the indentation level?
Yes, you can choose your preferred indentation (e.g., 2 or 4 spaces) to neatly format the JSON.
What is the difference between JSON minify and pretty print?
Minify removes all whitespace and line breaks, collapsing the JSON into a single line — useful when you need to reduce size for API requests. Pretty print adds indentation and line breaks to make the JSON easy for humans to read.
Is JSON with Korean or other Unicode characters supported?
Yes, UTF-8 encoding is fully supported, so JSON containing Korean characters or any other Unicode text can be parsed and formatted without issues. Unicode escapes (\uXXXX) are also handled correctly.
Can it handle large JSON files?
Processing happens within the browser's memory. Very large files (tens of MB or more) may slow down depending on browser performance. All processing is done entirely in the browser — nothing is sent to a server.
Can JSONL (JSON Lines) files also be parsed?
Yes, the JSONL format (.jsonl), where each line contains one JSON object, is automatically detected. Widely used for AI training datasets and log files, it displays a numbered list of objects along with the total count. Simply drag a .jsonl file into the input area.
Online JSON Parser & Formatter
JSON (JavaScript Object Notation) is the most common data exchange format. A JSON parser validates your JSON, pretty-prints it with indentation, and highlights syntax so you can spot errors instantly.
Features
- Real-time validation with 150ms debounce as you type
- Collapsible tree view — explore nested objects/arrays with
+/−toggles - Format / Minify — 2-space, 4-space, or tab indentation, or strip whitespace
- Error location — shows "line N, col M" for parse failures
- Lenient mode auto-recovery — fixes unescaped control characters, wrap-split tokens, trailing commas, and comments
- Recovery highlight — auto-recovered values get a 🟥 red outline so you can spot what changed
- Syntax highlighting — keys, strings, numbers, booleans, null colored distinctly
- Copy / Download — copy formatted output or save as
.jsonfile - JSONL auto-detection —
.jsonlfiles shown as a numbered object list
JSONL (JSON Lines) support
JSONL (JSON Lines, extension .jsonl or .ndjson) stores one JSON object per line. It is widely used for AI training datasets (ChatGPT, Claude fine-tuning) and server log files. When the input is JSONL, this parser auto-detects it, renders a numbered object list, and shows the total object count. Drop a .jsonl file onto the input box to parse it instantly; copy and download output stays in valid JSONL format (one object per line).
Lenient mode — auto-recovery for broken JSON
JSON copied from chat apps, email clients, or terminals often contains accidental line breaks that break JSON.parse. This tool auto-recovers 4 common cases:
- Control chars inside strings (
\n,\t) → replaced with spaces - Line breaks inside tokens (e.g.
847\n521,fal\nse) → rejoined - Trailing commas → removed
- Comments (
//,/* */) → stripped (URLs preserved)
When recovery applies, a yellow warning banner appears and recovered values are outlined in red.
Privacy: 100% client-side
Your JSON is never sent to any server. All parsing happens in your browser. Safe for JSON containing API keys, passwords, or sensitive customer data.
Common parse errors
- Unexpected token: missing quotes around keys, or missing comma/colon
- Unexpected end of input: unclosed
{}or[] - Trailing comma after the last item — not allowed in strict JSON
- Single quotes — JSON requires double quotes for strings
JSON syntax cheatsheet
- Keys must be strings wrapped in double quotes
- Values: string, number, boolean (true/false), null, object
{}, array[] - No comments (
//or/* */) in strict JSON
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