Does the viewer upload JSON?
No. The tree is built in the browser.
jfmt.dev
JSON Viewer
Paste JSON to explore it as a tree. Expand and collapse nodes locally — the document never leaves this device.
JSON formatter
Input
Output · preview.json
{ }
Run a tool to see a polished result here
Tree view vs pretty print
Pretty print is still text. The viewer turns objects and arrays into foldable nodes so large payloads are easier to scan. Switch to the homepage formatter when you need to copy indented JSON.
Related tools
FAQ
Can I edit in the tree?
Use the left editor to change text, then run the viewer again. The tree is for inspection.
What if JSON is invalid?
The viewer needs valid JSON. Validate or Repair first.