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

What’s new

- Fixed a startup crash on Android 7.x devices caused by a missing system library
- Fixed AWS Signature V4 authentication producing invalid signatures when the request URL contained special characters