Giant JSON Viewer: HAR & API

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 (basic) mock API server

JSON DIFF - COMPARE FILES

• Structural compare of two JSON / NDJSON files -- formatting and key order never count

• Detects moved and renamed data; repeated changes grouped into patterns

• Multi-GB tested; match list items by id; Markdown / NDJSON report export

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.

• 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.

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