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JSON OS

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JSON OS's own site

What JSON OS is

JSON OS is a free web workbench for editing JSON and writing or previewing Markdown. It requires no signup, and the maker says files are processed locally in a Web Worker, stored in IndexedDB, and not uploaded or sent to a server. The JSON editor offers tree, text, and table views, with independently switchable columns. It can format, beautify, minify, and sort data; validate it against JSON Schema with format checks; and repair common syntax problems such as trailing commas, unquoted keys, and unclosed brackets. Users can compare two documents side by side, apply MongoDB-style filters, and export JSON arrays to CSV with a UTF-8 BOM. The workspace supports up to three panes. Markdown Studio handles GitHub-Flavored Markdown, Mermaid diagrams, KaTeX math, highlighted code, and embeds from services including YouTube, Vimeo, CodePen, and GitHub Gist. It can export Markdown source, copy rendered HTML, or download a standalone HTML file. The maker says rendered HTML is sanitized and scripts and untrusted iframes are stripped.

Who it suits

JSON OS suits people who need to inspect, edit, validate, repair, compare, or query JSON in a browser, as well as write Markdown with previews and embeds. It is also suited to users who prefer local processing and no signup.

What it does well

  • Tree, text, and table editing views
  • JSON Schema validation and syntax repair
  • Side-by-side comparison and MongoDB-style filters
  • Markdown supports Mermaid diagrams and KaTeX
  • JSON and Markdown export options

What to know first

  • Workspace is limited to three panes
  • Available on web only

Limits

The JSON workspace supports up to three panes. The facts state no other free-plan quotas or usage limits.

Plans

PlanBilled and limitsPrice
FreeBrowser-based JSON editor and Markdown previewerFree

As jsonos.online lists them, read 8 Oct 2026. The maker's own page has the final word.

Getting started

  1. Open the JSON OS website in a browser; the site says signup is not required.
  2. Open or drop JSON files into the JSON editor.
  3. Open Markdown files by dragging and dropping them into Markdown Studio.
  4. Use the JSON editor's views, validation, repair, comparison, or query tools as needed.
  5. Export JSON arrays to CSV or export Markdown as source, rendered HTML, or a standalone HTML file.

Verdict

JSON OS brings a broad set of JSON editing and Markdown authoring tools into a browser workbench. Its local-processing approach, comparison and query tools, and varied Markdown exports make it useful for working with both formats in one place.

Questions

How much does JSON OS cost?

The listed Free plan costs nothing.

Do I need to sign up or upload files?

The site says the app requires no signup or uploads, and that there is no server processing. It says processing runs locally in a Web Worker, with data persisted in IndexedDB.

Which platform is available?

The listed platform is web.

What can JSON OS do with JSON files?

It can display and edit JSON in tree, text, or table views; format, minify, and sort keys; validate against JSON Schema; repair malformed JSON; compare documents; query with MongoDB-style filters; and export arrays to CSV.

What does Markdown Studio support?

It supports GitHub-Flavored Markdown, Mermaid diagrams, KaTeX math, syntax-highlighted code, and URL embeds including YouTube, Vimeo, CodePen, CodeSandbox, JSFiddle, GitHub Gist, and Twitter/X.

What are the workspace limits and export options?

The JSON workspace supports up to three panes. JSON arrays can be exported as CSV, while Markdown can be exported as source, copied as rendered HTML, or downloaded as standalone HTML.

Facts from JSON OS's own pages

Compare and query
The editor compares two documents side by side and supports MongoDB-style filters for querying JSON. · jsonos.online, 8 Oct 2026
CSV export
JSON arrays can be exported to CSV with a UTF-8 BOM for Excel compatibility. · jsonos.online, 8 Oct 2026
Embed integrations
Markdown URL embeds include YouTube, Vimeo, CodePen, CodeSandbox, JSFiddle, GitHub Gist, and Twitter/X. · jsonos.online, 8 Oct 2026
Embeds
Markdown URL embeds include YouTube, Vimeo, CodePen, CodeSandbox, JSFiddle, GitHub Gist, and Twitter/X. · jsonos.online, 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, 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, 8 Oct 2026
Formatting
The editor can format, beautify, minify, and sort JSON keys. · jsonos.online, 8 Oct 2026
JSON editing
The JSON editor supports tree, text, and table views, plus formatting, minifying, and sorting keys. · jsonos.online, 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, 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, 8 Oct 2026
Markdown exports
Markdown Studio can export Markdown source, copy rendered HTML, or download a standalone HTML file. · jsonos.online, 8 Oct 2026
Markdown features
Markdown Studio supports GitHub-Flavored Markdown, Mermaid diagrams, KaTeX math, syntax-highlighted code, and embeds. · jsonos.online, 8 Oct 2026
Markdown safety
The maker says rendered HTML is sanitized with DOMPurify and scripts and untrusted iframes are stripped. · jsonos.online, 8 Oct 2026
Output sanitization
Rendered Markdown HTML is processed through DOMPurify, and scripts and untrusted iframes are stripped. · jsonos.online, 8 Oct 2026
Privacy and signup
The site says the app requires no signup, uploads, or server processing. · jsonos.online, 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, 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, 8 Oct 2026
Repair
The editor repairs malformed JSON including smart quotes, trailing commas, unquoted keys, comments, and unclosed brackets. · jsonos.online, 8 Oct 2026
Schema validation
The editor validates JSON against JSON Schema using Ajv with format checks. · jsonos.online, 8 Oct 2026
Validation and repair
It validates JSON against JSON Schema and can repair issues including trailing commas, unquoted keys, and unclosed brackets. · jsonos.online, 8 Oct 2026
Workspace limit
The JSON workspace supports up to three panes. · jsonos.online, 8 Oct 2026

Where JSON OS stands on Freedom251

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