How it works
How to use the JSON Editor
Open or paste JSON
Paste, drop a file, open one, or load from a URL.
Edit with confidence
Errors are underlined as you type; fold sections, search with Ctrl/⌘+F and undo freely.
Format and save
Format in place with Ctrl/⌘+Enter, then copy or download.
A real editor, not a text box
The editor is built on CodeMirror: syntax highlighting, bracket matching, code folding, multiple cursors, search and replace, and full undo history. The output pane shows the formatted result, a searchable tree and statistics.
Built for developers
Why developers use it
Private by design
Everything runs locally in your browser. No uploads, no tracking of your data, no accounts.
Precise errors
Exact line and column, a plain-English explanation and a suggested fix for every syntax error.
Lossless formatting
Big integers, decimals and escapes are preserved byte-for-byte. Only whitespace changes.
Built for large files
A background worker, virtualised rendering and a fast custom parser keep big files smooth.
Tree explorer
Collapsible, searchable tree with JSONPath copying and jump-to-source.
Works offline
Install it as an app or keep using it without a connection once loaded.
FAQ
Frequently asked questions
Is my JSON saved?
Your last document is kept in this browser only (up to 1 MB) so it survives a refresh. Clear it any time.
Is my JSON sent to a server?
No. Parsing, validation, formatting and the tree view all run in your browser using JavaScript and a Web Worker. Your data never leaves your device. You can even use the tool offline once the page has loaded.
How large a JSON file can I open?
Files of tens of megabytes work well on a modern laptop. Processing runs in a background thread so the page stays responsive, the editor only renders what is visible, and the tree view is virtualised. The hard limit is 200 MB per file.
Does formatting change my numbers?
Never. Many online formatters use JSON.parse, which silently rounds big integers (like 64-bit IDs) and rewrites numbers such as 1.0 or 1e3. This tool keeps every number and string escape exactly as you wrote it — only whitespace changes.
Keep going
Related tools
- JSON FormatterFormat, validate and explore JSON
- JSON ValidatorFind and fix JSON syntax errors
- JSON ViewerExplore JSON as a searchable tree
- JSON CompareFind semantic differences between two JSON documents
- JSON DiffSide-by-side or unified line diff of two JSON files
- JSON SorterSort JSON keys alphabetically
- JSON to CSVConvert JSON arrays to CSV and CSV back to JSON
- JSON to XMLConvert JSON to XML and XML to JSON