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

#webdev #json #productivity #formatter

Remember JSON Formatter? The Chrome extension with 200K+ users that auto-formatted JSON in your browser? In mid-2026 it went closed-source, partnered with GiveFreely, and started injecting geolocation tracking plus donation popups into checkout pages. The developer's defense was "it's for charity." The community's response was a collective "uninstall immediately."

I'm a developer. I look at JSON all day — API responses, config files, debug dumps. I needed a replacement. So I tested every major JSON viewer on the market.

The Contenders

JSON Formatter (arnav-kr) — The spiritual successor

This is the most popular open-source fork. 60+ themes, collapsible toolbar, keyboard shortcuts for everything.

Good: Truly open source. Actively maintained. Works offline. The free tier is generous.

Catch: No large file support. Above ~5MB it starts to struggle. No JWT decoding, no advanced export formats. If you just need basic formatting, it's perfect. If you work with bigger data, keep reading.

JSON Viewer Pro (PatilWeb) — Power user's choice

300K+ users, 4.7 stars. Tree view, chart view, JSONPath with autocomplete, custom CSS. It's the most feature-rich free option.

Good: Breadcrumb navigation is genius. Chart visualization for numeric data. Active development (v7.1 as of October 2025).

Catch: Closed source. Smart UI is cool but sometimes doesn't trigger when you expect it to. Heavy — noticeably slower page loads on large JSON.

JSON Alexander (Wes Bos) — The celebrity pick

Built by Wes Bos specifically in response to the Formatter scandal. Clean, minimal, trustworthy by association.

Good: Dead simple. Interactive tree, path inspection, dark/light/auto themes. Built by someone the community trusts.

Catch: Feature-light compared to others. No search. No export. No large file handling. It's a formatter, not a toolkit.

JsonDiscovery — The different one

Instead of adding a toolbar, it transforms the entire page into an interactive explorer. Tree, table, and list views. Right-click context menus for copying paths and objects.

Good: Highest rated (4.88). Innovative UX. JORA query language with autocomplete.

Catch: Takes over the entire page — no way to see raw JSON side-by-side. Learning curve for the query syntax. Closed source.

Firefox Built-in — The one you already have

If you use Firefox, you already have a JSON viewer. Collapsible tree, syntax highlighting, search. It's fine.

Good: Zero install. Zero trust issues (it's the browser). Always there.

Catch: Chrome users are out of luck. No themes. No copy-to-path. No export. It's a viewer, not a tool.

The Pattern

Dealbreaker	arnav-kr	PatilWeb	Wes Bos	JsonDiscovery	Firefox
No large file support	✅		✅		✅
Closed source		✅		✅
Heavy / slow		✅
Too minimal	✅		✅		✅
Phones home?	❌	?	❌	?	❌

No tool was: fully open source + handles large files + privacy-guaranteed + feature-complete.

So I Built One

After two weeks of switching between tools depending on what I was doing, I built ClearJSON.

What it does

Formatting & Viewing:

Auto-detects JSON, JSON-LD, JSON:API, NDJSON — any JSON-like content type
Collapsible tree view with indent guides, element counts, and depth indicators
Syntax highlighting for all 7 JSON token types (strings, numbers, booleans, null, keys, punctuation, links)
10 free themes with automatic dark/light system following
Click-to-copy values, right-click for JSONPath or subtree
Auto-detected clickable links, hover-to-preview images (PNG/JPG/GIF/SVG/WebP)
Line numbers in raw view, status bar with node count/max depth/file size/parse time

Privacy — the reason I built it:

Zero network requests for free users. Not one. The extension has no analytics, no tracking, no accounts, no ads.
The Pro license verification is the ONLY network call, and only when activating a key.
All processing (parsing, formatting, rendering, search) happens on your device.

Pro features ($29 lifetime, no subscription):

Virtual scrolling for 500 MB+ JSON files (Web Worker + streaming parser)
JWT auto-decode — detects eyJ... tokens, inline displays header + payload, highlights expiry
Regex search with match navigation and full-document highlighting
Multi-format export: CSV, TSV, YAML, TypeScript type definitions (recursive inference)
20 additional premium themes (Monokai, Dracula, Nord, One Dark, Solarized, Catppuccin, Tokyo Night, Gruvbox, and more)
Custom keyboard shortcuts

The Tech Stack (for the curious)

Vanilla JS + IIFE module pattern. Zero frameworks, zero build steps. 28 files, ~59KB zipped.
CSS variable-driven theming. 30 themes defined as key-value pairs, injected at runtime via <style> tag.
Streaming parser (Pro): Web Worker receives raw text in chunks, builds a flat node array, main thread renders only visible rows via virtual tree. 10,000+ nodes renders in under a second.
JWT decode: Regex match → Base64Url decode (handles - → +, _ → /, missing padding) → JSON.parse header/payload → inline render in tree view.
TypeScript type generation: Recursive inference with duplicate structure deduplication. Generates proper interface blocks for nested objects.
License server: Cloudflare Workers + D1 (SQLite). 7-day cache + offline fallback. Only called during key activation/verification.

Honest Limitations

Chrome/Edge only. No Firefox version yet (Manifest V3 vs V2 differences).
Free tier limited to 2MB files. This is a deliberate choice — virtual scrolling is complex infrastructure, and it's how the Pro tier makes money.
No JSONPath query. JSON Query Tool and JSON Viewer Pro already do this well for free. I'm not going to build a worse version just to check a box.
No JSON Diff. Same reason — Just JSON and JsonKing do it better, for free.
Still early. ~43 installs as of writing. The product is solid, the user base is not.

Why $29 Lifetime?

JSON viewers have exactly zero marginal cost. No servers, no storage, no API calls. Charging a monthly subscription for one feels dishonest to me. The Pro tier unlocks features that took real engineering effort (virtual scrolling, streaming parser, JWT decode, multi-format export) — and a one-time payment reflects that value without the subscription fatigue.

Try it: ClearJSON on Chrome Web Store | Microsoft Edge Add-ons

Source: github.com/wayknow/clearjson (MIT)

What are you using to view JSON? Did I miss a good one?