Fast by design
Streaming parsing and bounded rendering keep large JSONL files responsive.
PRECISE JSONL VALIDATION
Find the exact line and character breaking your JSONL
Validate newline-delimited JSON without uploading it. Pretty JSON marks the first illegal character, reports its line and column, and keeps valid records visible.
SOURCEPaste textor
Paste anythingJSON, JSONL or NDJSON
Nothing uploadedLarge-file readyNo sign-up
ACTIONABLE ERROR LOCATIONS
Fix the source, not just the error message.
A generic parser exception is hard to use in a long record. Pretty JSON connects every validation result back to the editable source.
- 01
Validate on demand
Choose Auto or JSONL, then press Inspect data when the source is ready to check.
- 02
Locate the character
The editor highlights the first illegal character and reports its physical line and column.
- 03
Keep good records
Malformed JSONL lines are listed separately while valid rows remain searchable in the output table.
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.