Inspect large JSON without crashing your browser
JSON files from API dumps, database exports, and log aggregators can easily reach tens or hundreds of megabytes. Opening them in a text editor freezes the UI; pasting into an online formatter times out. This tool reads the file locally, splits it into navigable pages, and validates each page independently — so you can find exactly where a syntax error lives in a 50MB file without loading the whole thing into a single editor instance.
Getting started
- 1Drop a
.jsonfile onto the upload area, or click to browse. - 2The file is read in your browser and split into pages based on the lines/page setting.
- 3Navigate pages with the pagination controls. Each page shows a Valid or Invalid badge.
- 4Use Copy to grab the current page, or Download Full JSON to save the original file.
- 5Adjust lines/page (25–1000) to control how much content appears per page.
How it works
- Smart pagination — Arrays are split by items so no object is broken across pages. Non-array JSON is split by line count.
- Per-page validation — Each page is independently run through
JSON.parse. Green badge = valid, red = syntax error on that page. - Handles 100MB+ — The file is read with
FileReaderand paginated into small chunks. Only one page is rendered at a time. - Syntax-highlighted viewer — Each page renders in a read-only
CodeMirroreditor with full JSON syntax coloring. - Copy & download — Copy the current page to clipboard, download individual pages, or download the full original file.
- Drag & drop — Drop a file anywhere on the upload area. No file picker dialog needed.
- Completely offline — Everything runs in your browser. The file never leaves your device.
When you need this
- Debugging large API dumps — Find exactly which object in a 100K-element array has a syntax error.
- Database export inspection — Browse through MongoDB or PostgreSQL JSON exports page by page.
- Log file analysis — Navigate structured JSON log files that are too large for a text editor.
- Data validation — Verify JSON structure across all pages of a large dataset before importing.
Questions
What's the maximum file size?
There's no hard limit — it depends on your browser's available memory. Files up to 100MB work on most modern devices. The pagination ensures only one page is rendered at a time.
Is my file uploaded anywhere?
No. FileReader.readAsText() reads the file directly in your browser. There are no network requests, no server processing, no telemetry.
How are pages divided?
If the file contains a JSON array, items are grouped into pages (default 50 per page) so each object stays intact. For non-array JSON, the file is split by line count.
Can I download individual pages?
Yes. Each page has a Download button that saves just that page's content as a separate JSON file.