JSON editor online

Paste JSON, and the editor will format it and point at the error if the structure is broken. The file is not uploaded anywhere: everything happens in the browser.

Open the editor

What the editor does

Formats JSON with readable indentation
Shows the position of a syntax error
Collapses JSON into a single line when a compact form is needed
Keeps recent documents so you can return to them

Questions

Are my files uploaded to a server?: No. The editor works entirely in the browser, and the text of your document never leaves the device.
Do I need an account?: No. The editor is free and open without sign-up.
Where are recent documents stored?: In your browser, in IndexedDB. Clearing site data removes them, and they are not visible on other devices.