About NDJSON / JSONL Viewer

Parse and display newline-delimited JSON line by line. Part of the DevTools Surf developer suite. Browse more tools in the JSON collection.

Use Cases

• Data engineers inspecting log files from streaming pipelines
• ML engineers reviewing training data in JSONL format
• Backend developers debugging Elasticsearch bulk API payloads
• DevOps engineers parsing structured container log output

Tips

• Click individual lines to inspect deeply nested fields
• Filter lines by a key-value pair to find specific records
• Validate that every line is valid JSON before processing

Fun Facts

• NDJSON (Newline Delimited JSON) was popularized by tools like Apache Kafka and Elasticsearch's bulk API as a streaming-friendly alternative to JSON arrays.
• The JSONL format processes files line by line, enabling streaming of multi-gigabyte datasets that would crash parsers trying to load a single JSON array into memory.
• BigQuery, AWS Athena, and Snowflake all natively support NDJSON/JSONL as an import format, making it the de facto standard for data lake ingestion.

FAQ

What is NDJSON?

Newline-delimited JSON — each line is a standalone JSON object. Popular for streaming logs, ML datasets, and APIs that push many records (ElasticSearch bulk API, OpenAI streaming, BigQuery exports).

How is this different from a JSON array viewer?

NDJSON doesn't wrap lines in `[...]`, so you can stream-parse line by line without buffering the whole file. Huge log files stay memory-friendly. The viewer respects this structure.

Can I convert NDJSON to a JSON array?

Yes — the tool has a 'wrap as array' toggle. Useful when pasting into tools that expect standard JSON, though you lose the streaming benefit.

What happens if one line is invalid?

Only that line is flagged; the others render normally. This is NDJSON's design — resilient to partial corruption in long log files.