JSON Editor Online - Edit & Format JSON Online | SmartJson
Free online JSON editor. Edit, format, validate and beautify JSON data with syntax highlighting and real-time error detection.
Key Features
- ✅ Real-time syntax highlighting
- ✅ Inline error detection
- ✅ JSON formatting
- ✅ Tree view navigation
How to Use
- Start typing or paste your JSON
- Errors appear shortly after you pause, with line numbers
- Switch between raw text and tree view as needed — edits stay in sync
- Use the format button to beautify
- Export the corrected JSON
Expert FAQ
- How is this different from the JSON Formatter or JSON Validator?
Those are single-pass, paste-and-process tools built around a document you already consider close to final. The editor is for iterative authoring — building or restructuring a JSON document over many edits, where syntax highlighting and error detection need to update live on every pause rather than only being checked once at the end. - Does it flag an error while I'm still in the middle of typing a value?
No — validation is debounced to run shortly after you pause rather than on every keystroke, since a document is expected to be transiently "incomplete" while you're actively typing (an open quote before you've typed the closing one, for instance), and flagging every intermediate state as an error would make active editing unusable. - Can I switch between raw text editing and a tree view without losing my place?
Yes — both views operate on the same underlying parsed document, so edits made in the tree view (adding a key, changing a value) are reflected in the text view and vice versa, rather than being two disconnected representations you have to manually keep in sync. - Is there a limit to how large a document I can comfortably edit here?
The editor is built for typical hand-authored or hand-edited JSON — config files, API payload examples, test fixtures — rather than multi-megabyte machine-generated exports. For files large enough that live syntax highlighting and validation would lag on every keystroke, the Large JSON Reader's chunked-loading approach is the better fit, though it's read-oriented rather than built for active editing.
Technical Details
A JSON editor differs from single-pass tools like the Formatter or Validator in its update model: rather than one paste-and-process action, it re-validates on a short debounce after each pause in typing, so syntax highlighting and inline error markers stay current through an entire editing session. This is deliberately tolerant of transiently "incomplete" states — an object with an open brace and no closing one yet is normal mid-edit, not something worth interrupting you over — the same tolerance a code editor extends to unmatched brackets while you're still typing. The tree view and raw text view operate on one shared parsed representation rather than being independently maintained: editing a value in the tree updates the underlying document the text view reflects, and typing directly in the text view updates what the tree renders. This matters for anyone who thinks better navigating a large object visually but prefers typing raw JSON for small, precise edits — switching between the two doesn't require manually re-syncing or losing unsaved changes. This editor targets the size range of hand-authored and hand-edited JSON — configuration files, API request/response examples, test fixtures — where live validation on every keystroke is cheap. For genuinely large, machine-generated files where that live-update cost would itself introduce lag, the Large JSON Reader's chunked-loading, lazy-rendering approach is the better tool, though it's built for reading and searching rather than active editing. Once you're happy with a document here, the JSON Validator gives a final structural confirmation outside the live-editing context.