Fast by design
Streaming parsing and bounded rendering keep large JSONL files responsive.
FAST LARGE-FILE INSPECTION
Open large JSONL files without freezing your browser
Stream large newline-delimited files through a background worker, keep the interface responsive and inspect a virtualized table without sending data to a server.
SOURCEPaste textor
Paste anythingJSON, JSONL or NDJSON
Nothing uploadedLarge-file readyNo sign-up
DESIGNED FOR LARGE INPUTS
Parse the full file. Render only what matters.
Pretty JSON separates parsing from rendering so a large source does not become thousands of expensive page elements.
- 01
Stream the file
JSONL is decoded incrementally instead of copying the complete file into a visible text editor.
- 02
Bound the preview
The complete file is processed while a capped set of records and fields is retained for exploration.
- 03
Virtualize the table
Only visible rows are mounted, keeping scroll and field selection responsive as the dataset grows.
THE NICE WAY TO READ JSON
A calmer way to inspect data.
Useful defaults, clear hierarchy and no visual noise between you and the payload.
Private on-device
Your data stays inside the browser. There is no upload step or account.
Explore records quickly
Search loaded JSONL records, choose visible fields and expand any row as formatted JSON.
Actionable errors
Malformed lines are explained while valid records remain available.
BUILT FOR MESSY REAL DATA
More than a formatter.
Find structural problems before they turn into failed imports, brittle pipelines or hard-to-debug model runs.
Large JSONL logs
Scan records, search the bounded preview and keep valid rows visible when individual lines are malformed.
Training datasets
Spot missing keys and changing value types before handing a JSONL dataset to a training or evaluation job.
API & database exports
Understand unfamiliar payloads through searchable records and nested field paths without uploading sensitive data.
GOOD TO KNOW
Questions, answered.
Does Pretty JSON upload my files?
No. Parsing, search and formatting run locally in your browser. The current version has no file-upload endpoint.
How does it stay responsive with large JSONL files?
JSONL is streamed through a background worker. Only the first 5,000 records are retained for preview, and the table renders only visible rows.
Is a large JSON file the same as JSONL?
No. JSONL can be processed one record at a time. A regular JSON document is one value, so this version applies a 128 MB safety limit and recommends JSONL for larger datasets.
What appears in Output?
Output is reserved for JSONL. It provides a searchable table, selectable fields and expandable formatted rows; regular JSON stays in the source editor with formatting tools.