JSON vs NDJSON: When to Use JSON Lines
Compare JSON arrays and newline-delimited JSON for logs, streaming APIs, exports, and incremental processing.
NDJSON stores one complete JSON value on each line. A conventional JSON export often stores all records inside one array. Both use JSON syntax for individual values, but they differ in how records are framed and processed. That difference matters when an export grows beyond what you want to load into memory.
Choose arrays for complete documents
A JSON array is convenient for small API responses and configuration that should be validated as one document. Standard JSON parsers accept it directly. The opening bracket, separators, and closing bracket are part of the document, so appending records to a file requires maintaining valid array syntax. A partially written array may not parse as a complete JSON document.
Choose lines for record streams
With NDJSON, a reader can process a completed line without waiting for the end of the file. This works well for log pipelines and batch exports. Each line must contain a complete JSON value; formatting one record across several physical lines breaks that framing. Newlines inside string values must be escaped using JSON syntax rather than inserted literally.
Understand conversion costs
Converting an array to NDJSON removes only the outer array and serializes each member independently. Converting back collects values into a new array. Our browser converter loads the full input in memory, so it is a convenient conversion tool rather than a streaming engine for multi-gigabyte files. Use a streaming parser or command-line pipeline when file size exceeds a comfortable browser workload.
Worked example
JSON: [{"id":1},{"id":2}]
NDJSON:
{"id":1}
{"id":2}Are NDJSON and JSON Lines equivalent?
They share the one-JSON-value-per-line approach. Check the receiving system for conventions about blank lines, final newlines, and accepted value types.
Reference and further reading
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How to Parse JSON Lines and Find Invalid Records
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How to Flatten Nested JSON Without Losing Structure
Flatten nested JSON for exports and debugging while preserving arrays, empty containers, and keys that contain dots.
JSON Pointer Explained: Paths, Arrays and Escaped Keys
Learn JSON Pointer syntax, including /0 array indexes, ~0 and ~1 escaping, and the empty root pointer.