Validate your JSON.
safe · secure · no server · works offline · fast
…or just start typing at the cursor.
safe · secure · no server · works offline · fast
…or just start typing at the cursor.
Drop a .json file and OmniViewer tells you at once whether it
is valid JSON — and if it isn’t, where it breaks. A
bar above the formatted view reports the verdict, the document’s root
type (object, array, …) and its size; on a bad file it surfaces the parse
error. It all runs locally in a Web Worker, with no upload and no server.
Once it’s valid, the same view pretty-prints and syntax-highlights the document, and the other tabs convert it to YAML or CSV, compute stats, or drop to raw and hex. Past a size threshold the check is skipped to stay fast, and it says so.
It’s one lens on OmniViewer’s JSON Viewer & Formatter — Beautify & Convert .json: drop a file and every tab is one click away. OmniViewer opens every file format, entirely in your browser — no upload, no server.
No. OmniViewer is a static page with no server-side processing: your .json file is read directly by your browser, and every tab — formatting, YAML, CSV and stats — runs locally in a Web Worker. The file never leaves your computer.
The raw and hex views are windowed — they read only the bytes needed to paint the screen — so they open files of effectively unlimited size, up to 20 GB and beyond; the engine behind them has been tested in-browser with a 40 GB file. The formatted view and the conversions (YAML, CSV) and stats process the document in memory, so on very large files they work on a bounded prefix and tell you when they do. The validity check above the view is skipped past a size threshold for the same reason.
Yes. The YAML tab renders the document as a block-style YAML file, quoting strings only where YAML requires it. The CSV tab flattens an array of objects into an RFC 4180 table whose columns are the union of every object’s keys, with nested values encoded into the cell. Both offer copy and download.
Yes. The JSON generator at /s/json/generator builds a synthetic JSON file of any size up to 50 GB — you pick the target size — and streams it straight to disk via the File System Access API without uploading anything. On browsers without that API (Firefox, Safari) it falls back to a Blob download, which is fine for modest sizes.
CSV is a table, so it only makes sense when the JSON is an array of objects (rows). If your document is a single object, a plain array of numbers, or anything else that isn’t a list of records, the CSV tab isn’t shown — the Formatted, YAML and Stats tabs still are.
Yes. A bar above the raw and formatted views reports whether the file parses as valid JSON (and its root type — object, array, and so on) or, if it doesn’t, the parse error. Past a size threshold the check is skipped to stay fast, and it says so.
JSON is defined by IETF RFC 8259 and, identically, by ECMA-404. Standard JSON does not allow comments or trailing commas — that strictness is deliberate, to keep it safe to exchange between systems. Variants like JSON5 and JSONC add comments, but they are not standard JSON.
Same engine, same authors. OmniViewer is the universal front door for any file, with a JSON toolkit for everyday files. fastjsonviewer.com is the specialised tool for very large JSON — collapsing, searching, querying and streaming multi-gigabyte documents.