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Show HN: Jsonl Viewer – Desktop app for 10M+ rows with nested flattening
- hilti 11mo agoHey HN! Author here. I built this after struggling with Excel/Pandas for large JSONL log files from IoT devices. The data had deeply nested objects and millions of rows. The key challenge was speed + usability. I wanted to just double-click a file and see my data instantly, with the ability to filter nested fields. How it works: 1. Multi-threaded parsing with simdjson's on-demand API 2. Automatic flattening of nested objects into dot notation 3. Virtual scrolling (only render visible rows) 4. Lazy extraction (parse nested JSON on display, not on load) Example - this JSON: {"user": {"profile": {"email": "test@example.com", "age": 30}}} Automatically becomes filterable columns: - user.profile.email - user.profile.age No configuration needed. Just works. Tech stack: C++ with simdjson for parsing, ImGui for UI, HelloImGui for cross-platform support. Native binary, not Electron (~15MB app). Performance: 5GB file with 10M records loads in ~2 seconds on M2 Mac. Tested up to 50M rows without issues. Available for Mac (Silicon/Intel) and Windows. Linux coming soon. Launch discount: 50% off with code HN50 for next 48 hours. - Mac: https://iotdatasystems.gumroad.com/l/jsonlviewerpro_mac https://iotdatasystems.gumroad.com/l/jsonlviewerpro_mac - Windows: https://iotdatasystems.gumroad.com/l/jsonlviewerpro_win https://iotdatasystems.gumroad.com/l/jsonlviewerpro_win Happy to answer questions about the implementation or design decisions! Use cases I've heard so far: - DevOps analyzing structured logs - Data scientists previewing datasets - Backend developers debugging API responses - IoT engineers reviewing device telemetry