MergeJSON

The toolkit

All JSON tools, in one place.

A complete set of free, private JSON utilities — formatting, validation, key sorting, stringifying, mock data generation, flattening, unflattening, and conversion to CSV, Excel, JSONL, Base64, HTML tables, Markdown tables, and back. Every tool runs entirely in your browser, with no uploads and no file-size cap.

One private JSON toolkit for every job

These online JSON tools share a single principle: everything runs client-side, so your data is never uploaded. Use the formatter to pretty-print, the validator to catch syntax errors with an exact line and column, the minifier to shrink payloads, JSON Sort to sort JSON keys A to Z or Z to A, JSON Stringify to escape JSON for embedding in code or database fields, and the viewer to explore structure as a tree. Flatten nested data with JSON Flatten or rebuild nested JSON from flat keys with JSON Unflatten. Need a mock data? Use JSON Generator to create template-driven mock JSON data. Need a different format? Convert JSON to CSV, JSON to JSONL, JSON to Base64, JSON to HTML Table, JSON to Markdown Table, CSV to JSON, JSONL to JSON, JSON to Excel, and Excel to JSON — each with control over shapes, delimiters, and nested data. New here? Start with how it works or the JSON guides blog.