JSON OS vs JSONZen

JSON OS is a free, browser-based workbench that pairs a JSON editor with Markdown Studio, a Markdown previewer. The maker says it needs no signup and that processing runs locally in a Web Worker, with data stored in IndexedDB and nothing leaving the device. The JSON workspace supports up to three panes and can open or accept dropped files. Data can be viewed and edited as a tree, text or table, with table columns switched independently. The editor formats, beautifies, minifies and sorts JSON keys, validates against JSON Schema with Ajv format checks, and repairs malformed input such as smart quotes, comments and unclosed brackets. It compares two documents side by side and supports MongoDB-style filters; JSON arrays can be exported to CSV with a UTF-8 BOM. Markdown Studio supports GitHub-Flavored Markdown, Mermaid, KaTeX, highlighted code and embeds from services including YouTube, Vimeo and GitHub Gist. It sanitizes rendered HTML through DOMPurify, stripping scripts and untrusted iframes. Markdown can be exported as source, copied as rendered HTML or downloaded as standalone HTML.

JSONZen is a browser toolkit for formatting, validating, comparing, querying and converting JSON. Its tools also include minification, a tree view, JWT decoding and code generation for TypeScript, Zod, Pydantic v2 and JSON Schema. The site says core tools run in the browser and require no signup. Validation supports JSON Schema drafts 07, 2019-09 and 2020-12, with errors reported by path. Queries can use JSONPath and JMESPath; jq querying is listed as a Pro tool. Share links place their payload in the URL fragment rather than on JSONZen’s servers. Free share links allow up to 32 KB, and Free users can store three snippets locally per browser. Pro adds encrypted cloud-synced snippets, with manual syncing per snippet and a 2 MiB ciphertext limit per snippet. The listed Free plan is free, billed Forever. Pro is listed at $1.00 USD once for 30 days as a launch promotion, with no auto-charge; the pricing note lists paid plans from $5/mo. The CLI is included free.