Open a tab and paste a complete JSON document into its editor. Change the value you need, then use Format to make the active document readable. With automatic validation enabled, inspect the error state after each change instead of assuming that highlighted text is valid JSON. The example below changes a numeric count and shows the formatted document you can download. Copy the active result only after it parses successfully.
Use separate tabs for independent documents and undo or redo to move through a tab's changes. Browser autosave stores editor state locally; that is separate from an account save. Uploads above 50MB are rejected. Keep your own backup for important work because clearing browser storage removes local state, and browser memory can limit smaller documents too.
Edit {"count":1} to {"count":2}, then Format:
{
"count": 2
}
Real-time validation catches syntax errors as you type — missing commas, unmatched brackets, invalid values. A plain text editor won't tell you your JSON is broken until you try to parse it.
Uploads above 50MB are rejected. The editor reads the document into browser memory, so smaller inputs can still become difficult to edit or validate. Keep a backup of important files and check the active tab before downloading. Minification changes presentation rather than extending the upload limit or guaranteeing responsiveness.
The editor works with standard JSON (RFC 8259). JSON5 features like trailing commas, comments, and unquoted keys are not supported since most APIs and parsers require strict JSON.
Yes. The editor maintains a full undo/redo history. Use Ctrl+Z (Cmd+Z on Mac) to undo and Ctrl+Shift+Z to redo. The history persists until you close the page.
Processing runs in your browser. Choosing Share uploads the selected tool state; anyone with the link can open it. Signing in to save sends content to your account library and records save history. Review the selection before either action. Closing the page does not delete those copies. Copying locally does not create a server share.