Giant JSON Viewer: HAR & API

Kotysoft

In-app purchases

About this app

A JSON viewer and analysis toolkit built for files that crash everything else.

Supports: json jsonl ndjson har CBOR MsgPack md

Made for developers, analysts, and QA engineers who work with massive datasets -- multi-GB logs, database dumps, API responses -- directly on Android. No ads, No cloud, no account, no limits*.

While most viewers struggle above 50MB, GiantJSON Viewer uses a native Rust engine to handle multi-gigabyte files without running out of memory. Built and maintained by a solo indie developer.

BUILT FOR PERFORMANCE
• Large JSON Support: Open files that other viewers can't handle
• SIMD accelerated Indexing: First load builds an index for instant navigation
• Memory Safe: Designed to prevent Out-Of-Memory crashes on any device
• Rust + SIMD Core: Native speed, not a JavaScript wrapper

DEVELOPER TOOLKIT
• SQL & CSV Export: Convert to SQL queries or CSV tables
• Data Masking: Redact selected fields during export
• Advanced Filter: Visual query builder with field-level conditions
• Search & Regex: Full-text search / filter with regex support
• GenAI Regex Builder: Describe what you need, AI writes the regex
• JSON Path Navigation: Jump directly to any node
• Schema Export: Export structure as JSON Schema, TypeScript, or Markdown
• Auto-prettify and syntax highlight in RAW text mode with tree mode collapse feature

API CLIENT
REST and GraphQL client, right on your phone:
• GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS + GraphQL queries
• Auth: Basic, Bearer, OAuth 2.0 (with PKCE), AWS Signature V4
• Postman collection import with folder structure and variables
• Environment support with variable precedence
• File attachments, binary uploads, session cookies
• Import/export via cURL
• Responses open directly in the viewer

HAR ANALYZER
Drop a .har file and get a full network analysis dashboard:
• Overview stats: request count, response times, errors, transfer size
• Timing breakdown, status distribution, domain summary
• Filter by method, status, content type, domain, or response time
• Request detail tabs: headers, cookies, body, timing waterfall, TLS
• Clone any request to API Client or copy as cURL

BASIC MOCK API SERVER
Turn your phone into a mock API server:
• Custom endpoints with method, status code, and headers
• Point responses to local files
• Web dashboard with request logging

3 VIEW MODES
• TEXT: Raw view with syntax highlighting, formatting and collapsible tree
• BROWSER: Stream through gigabytes like a folder structure
• STRUCTURE: Visualize data structure as a graph to understand its shape

HOSTED WEB TOOLS - a private toolset on your local network
• File Transfer -- drag and drop files, no cables, no cloud, no size limit
• JWT Decoder -- decode tokens, inspect header and payload, check expiry
• Timestamp Converter -- epoch to human-readable and back
• JSON Formatter -- format, minify, stringify, unescape
• URL Encoder -- encode, decode, and parse URLs with query breakdown

MORE
• Markdown Viewer: Render .md files
• Bookmarks: Save locations in huge files to find later in Browser Mode
• Hide Paths: hide irrelevant elements from view
• Unescape & Prettify: Fix serialized or minified JSON
• JSON Schema Validator: Validate against a schema file with detailed error report

PRIVATE & SECURE
Everything runs locally on your device.
• All search, analysis, and export happens offline
• No cloud uploads, no account registration
• GenAI Regex only calls AI to generate patterns -- your data never leaves
• (!) Anonymous crash reports and usage statistics collected for development (can opt out)

This app is a one-person project under active development. If you find it useful, a review on Google Play helps more than you'd think. And if
something isn't working right, the in-app feedback goes straight to the developer.

*Theoretical limits are 1TB, 255 depth, storage space, and some RAM requirement. ~100GB tested

Ratings and reviews

This JSON Viewer app is a game-changer! It’s super easy to load and view large JSON files, and the interface is clean and fast. If you handle JSON often, I’d definitely recommend giving it a try!

This app works flawlessly! It effortlessly opens large JSON files without any issues. Highly recommended for anyone dealing with massive datasets!

Doesn't open simple json files. Possibly because it's 60 kb

What’s new

NEW: ~10 most common type detection for values in browser mode