Edit JSON in a syntax-highlighting editor with live error markers, then format, minify and download — entirely in your browser. Free, no sign-up — runs locally in your browser.
Your work is auto-saved in this browser only, so a refresh won't lose it. Nothing is uploaded.
Why edit JSON in a dedicated editor?
Most JSON is not written once and read once — it is drafted, pasted
from somewhere half-broken, adjusted, re-checked and adjusted again.
A plain text box makes that loop miserable: no line numbers to
navigate by, no highlighting to separate keys from values, and no
feedback until you run a separate check. This editor closes the
loop. Syntax highlighting keeps structure visible at a glance, the
gutter marks the line where parsing fails while you type,
and the status bar always states the verdict in words — valid, or
invalid with the line and column of the first error.
How to use this editor
Type or paste a document, upload a .json file, or press Load sample. Restored drafts from earlier visits appear automatically.
Watch the status bar and the gutter markers as you work — the document is linted on every change.
Press Format in place to rewrite the document with consistent indentation (2, 3 or 4 spaces, or tabs) without leaving the page, or Minify in place to collapse it to one line.
Take the document away with Copy, Download or Print. Everything happens in your browser; nothing is uploaded.
Editor, checker or formatter?
Editor (this page) — you are writing or actively fixing a document and want live feedback while you work.
Checker — you only need a verdict and an error location for a finished document; nothing is edited.
Formatter — you need the one-shot transforms plus the tree view, graph view and the announced repair pass for badly broken input.
Frequently asked questions
How is a JSON editor different from a JSON formatter?
A formatter is a one-shot transform: paste, press a button, copy the result. An editor is a workspace: the document stays in a real editing surface with syntax highlighting, line numbers and error markers that update as you type, so you can build or fix a document iteratively and format or minify it in place when it is ready.
What do the error markers in the gutter mean?
The editor lints as you type. A marker on a line means the document is not valid JSON and the problem is at or before that position — unclosed strings and trailing commas usually surface exactly on their line. The status bar under the editor states the verdict in words and gives the line and column of the first error.
Is my document uploaded or stored on a server?
No. Editing, linting and formatting all happen in your browser. The only copy kept anywhere is a draft in this browser's local storage, kept for seven days so a refresh does not lose your work — it never leaves this device, and the Clear saved draft button removes it.
Can the editor handle very large JSON files?
It stays responsive for documents up to a few megabytes, which covers the vast majority of payloads and config files. Beyond that, a desktop editor will serve you better than any in-browser tool — the lint pass runs on every keystroke by design.
Does Format change my data?
No. Format only rewrites whitespace: it parses the document and writes it back with consistent indentation (your key order is preserved unless the formatter's sort option is used there). If the document is invalid, Format refuses and the status bar tells you where the first error is instead.
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