I Tested Every JSON Viewer After the Formatter Scandal. Here's What I Found.

In mid-2026, the once-popular Chrome extension JSON Formatter, which had over 200,000 users, went closed-source and started injecting geolocation tracking and donation popups into checkout pages. This sparked a collective response from the developer community, leading to the search for alternative JSON viewers. The reporter, a developer who frequently works with JSON, conducted tests on various JSON viewers in the market.

The Contenders included JSON Formatter (arnav-kr), JSON Viewer Pro (PatilWeb), JSON Alexander (Wes Bos), JsonDiscovery, and the built-in Firefox JSON viewer. Each of these had their strengths and weaknesses. While JSON Formatter was open-source and truly maintained, it struggled with large files. JSON Viewer Pro offered a plethora of features, but it was closed-source and sometimes heavy on page loads.

JSON Alexander, built by Wes Bos, was straightforward but lacked advanced features. JsonDiscovery transformed the entire page into an interactive explorer, but it took over the entire page and had a steep learning curve. The built-in Firefox JSON viewer was convenient but lacked customization options.

After trying out these options, the reporter found that none of them fully satisfied their criteria of being fully open-source, handling large files, being privacy-guaranteed, and being feature-complete. So, the reporter decided to build their own solution: ClearJSON. ClearJSON offers formatting and viewing capabilities, including auto-detection of various JSON-like content types, a collapsible tree view, syntax highlighting for JSON token types, 10 free themes with an automatic dark/light system, click-to-copy values, right-click for JSONPath or subtree, auto-detected clickable links, hover-to-preview images, and line numbers in the raw view.

Privacy is a key feature of ClearJSON, as it ensures zero network requests for free users, no analytics, no tracking, no accounts, and no ads. The Pro license verification is the only network call, which happens only during activation. All processing occurs on the user's device, ensuring privacy. The Pro features include virtual scrolling for large JSON files, JWT auto-decode, regex search with match navigation and full-document highlighting, multi-format export, premium themes, custom keyboard shortcuts, and more.

The reporter's own tech stack for ClearJSON includes Vanilla JS, IIFE module pattern, zero frameworks, and zero build steps. The extension is ~59KB zipped, uses CSS variables for theming, and includes a streaming parser in the Pro version for handling large files efficiently. The reporter faced some honest limitations, such as Chrome/Edge compatibility, the free tier's 2MB file limit, and the absence of JSONPath query or JSON Diff features.

Despite these limitations, ClearJSON has taken off with over 10,000 installs as of writing, though the user base is still early. The reporter justifies the $29 lifetime Pro tier by emphasizing the zero marginal cost of JSON viewers and the real engineering effort required for Pro features.