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JSON OS
What it is
JSON OS is a free, browser-based workbench combining a JSON editor with Markdown Studio, and its maker says no signup, uploads, or server processing are required. Processing runs locally in a Web Worker, with data stored in IndexedDB, and the workspace supports up to three panes. JSON can be viewed and edited as a tree, text, or table, with independently switchable columns. The editor formats, beautifies, minifies, sorts keys, validates against JSON Schema using Ajv format checks, and repairs malformed data such as smart quotes, trailing commas, unquoted keys, comments, and unclosed brackets. Two documents can be compared side by side, with sync scrolling and ignore rules, while MongoDB-style filters query data. JSON arrays export to CSV with a UTF-8 BOM. Markdown Studio supports GitHub-Flavored Markdown, Mermaid, KaTeX, highlighted code, and URL embeds. Rendered HTML is sanitized with DOMPurify; scripts and untrusted iframes are stripped. Markdown exports include source, rendered HTML, or standalone HTML.
For and against
For
- No signup or server processing
- Tree, text, and table JSON views
- Schema validation and malformed-data repair
- Side-by-side comparison and filters
- Markdown diagrams, math, and embeds
Against
- Workspace supports up to three panes
- Available only on the web
- No pricing or usage limits beyond the free plan are stated
The verdict
JSON OS brings substantial JSON editing and Markdown publishing tools into a browser workspace. Its local-processing approach and file import/export options suit users who prefer working without uploads.
Who it suits
It suits people who need local browser tools for JSON cleanup, comparison, querying, validation, and Markdown authoring.
Plans and prices
Free
Browser-based JSON editor and Markdown previewer
Read 8 Oct 2026 · jsonos.online
On the record
- Compare and query
- The editor compares two documents side by side and supports MongoDB-style filters for querying JSON.jsonos.online · read 8 Oct 2026
- CSV export
- JSON arrays can be exported to CSV with a UTF-8 BOM for Excel compatibility.jsonos.online · read 8 Oct 2026
- Embed integrations
- Markdown URL embeds include YouTube, Vimeo, CodePen, CodeSandbox, JSFiddle, GitHub Gist, and Twitter/X.jsonos.online · read 8 Oct 2026
- Embeds
- Markdown URL embeds include YouTube, Vimeo, CodePen, CodeSandbox, JSFiddle, GitHub Gist, and Twitter/X.jsonos.online · read 8 Oct 2026
- Exports
- JSON arrays can be exported to CSV, and Markdown can be exported as source, copied as rendered HTML, or downloaded as standalone HTML.jsonos.online · read 8 Oct 2026
- File use
- Users can open or drop JSON and Markdown files, and the Markdown Studio can import .md files by drag and drop.jsonos.online · read 8 Oct 2026
- Formatting
- The editor can format, beautify, minify, and sort JSON keys.jsonos.online · read 8 Oct 2026
- JSON editing
- The JSON editor supports tree, text, and table views, plus formatting, minifying, and sorting keys.jsonos.online · read 8 Oct 2026
- JSON views
- The JSON editor can display and edit data in tree, text, or table view, with columns switchable independently.jsonos.online · read 8 Oct 2026
- Local processing
- The maker says processing runs locally in a Web Worker, data is persisted in IndexedDB, and nothing leaves the device.jsonos.online · read 8 Oct 2026
- Markdown exports
- Markdown Studio can export Markdown source, copy rendered HTML, or download a standalone HTML file.jsonos.online · read 8 Oct 2026
- Markdown features
- Markdown Studio supports GitHub-Flavored Markdown, Mermaid diagrams, KaTeX math, syntax-highlighted code, and embeds.jsonos.online · read 8 Oct 2026
- Markdown safety
- The maker says rendered HTML is sanitized with DOMPurify and scripts and untrusted iframes are stripped.jsonos.online · read 8 Oct 2026
- Output sanitization
- Rendered Markdown HTML is processed through DOMPurify, and scripts and untrusted iframes are stripped.jsonos.online · read 8 Oct 2026
- Privacy and signup
- The site says the app requires no signup, uploads, or server processing.jsonos.online · read 8 Oct 2026
- Product
- JSON OS is a free, browser-based workbench with a JSON editor and Markdown previewer; the maker says it requires no signup.jsonos.online · read 8 Oct 2026
- Query and compare
- It supports MongoDB-style JSON filters and side-by-side document comparison with sync-scroll and ignore rules.jsonos.online · read 8 Oct 2026
- Repair
- The editor repairs malformed JSON including smart quotes, trailing commas, unquoted keys, comments, and unclosed brackets.jsonos.online · read 8 Oct 2026
