Are blank lines in the input a problem?

No, blank lines are skipped entirely and don't count as a parse failure or produce an extra array item, which matches how most real-world JSONL files, log exports especially, tolerate stray blank lines between records.

What happens if one line has invalid JSON?

Parsing stops at that line and the error message is prefixed with the exact line number (e.g. "Line 3: ..."), reusing the underlying JSON parser's own error text, so you can jump straight to the problem line in the source file.

Does every line need to contain an object?

No, JSON Lines allows any valid JSON value per line, a string, number, boolean, null, array, or object, and this parser accepts whatever each line actually contains.

Is the output array pretty-printed?

Yes, the collected array is formatted with the standard 2-space (or custom) indentation used across this site's JSON tools, unlike the compact one-line-per-record JSONL input.

JSONL to JSON Converter - Convert JSON Lines to a JSON Array

Overview

Introduction

JSON Lines files, exported logs, streaming API dumps, bulk-export files, are easy to produce but awkward to inspect as a whole, since most JSON tooling expects a single JSON document, not one per line.

This tool reads that line-per-record format and collects it into one standard JSON array you can format, diff, or feed into any other JSON tool.

What Is JSON Lines to JSON Converter?

A line-oriented parser that splits input text on newlines, skips blank lines, and runs JSON.parse on each remaining line individually, collecting every successfully parsed value into an array in original order.

It doesn't require every line to be the same shape or type, each line is parsed and accepted independently.

How JSON Lines to JSON Converter Works

The input is split on newline characters, and each non-blank line is parsed with JSON.parse in turn; a successful parse appends that line's value to the result array.

If a line fails to parse, the tool stops immediately and returns an error whose message is `Line ${n}: ${the underlying SyntaxError's message}`, giving you the exact 1-based line number where parsing broke.

When To Use JSON Lines to JSON Converter

Use it to turn a JSONL log export or streaming API dump into a single JSON array you can format, search, or diff with standard JSON tools.

It's also useful for validating a JSONL file line-by-line and getting a precise line number for the first malformed record.

Often used alongside JSON to JSON Lines Converter, JSON Formatter & Beautifier and JSON Validator.

Features

Advantages

Points to the exact line number of the first invalid line rather than failing with a generic, file-wide error.
Tolerates blank lines between records without treating them as errors.
Accepts any valid JSON value per line, not just objects, matching the full flexibility of the JSON Lines spec.

Limitations

Parsing stops at the first invalid line rather than collecting and reporting every error in the file at once.
Very large JSONL files are parsed entirely in the browser, so extremely large inputs are bounded by available memory.

Examples

Two records collected into an array

Input

{"a":1}
{"b":2}

Output

[
  {
    "a": 1
  },
  {
    "b": 2
  }
]

Each line is parsed independently and pushed into the resulting array in order.

An invalid line reports its exact number

Input

{"a":1}
not json
{"b":2}

Output

Line 2: Unexpected token 'o', "not json" is not valid JSON

Parsing fails on line 2 specifically, with the underlying JSON parser's own message preserved.

Best Practices & Notes

Best Practices

Fix the reported line and re-run the conversion rather than assuming later lines are also valid; parsing stops at the first failure.
Use JSON to JSON Lines afterward if you need to convert the resulting array back to JSONL after editing it.
For very large JSONL log files, consider filtering to a smaller sample first if the browser struggles with the full file.

Developer Notes

Each line is parsed with its own try/catch around JSON.parse rather than a single parse over the whole file, which is what lets the error message carry a precise line number, the underlying SyntaxError's message is reused as-is (not reformatted), since V8's own message already names the offending token.

JSON Lines to JSON Converter Use Cases

Converting a JSONL log export into a single JSON array for inspection
Validating a JSON Lines file and locating the first malformed record
Preparing streaming API output for tools that only accept a single JSON document

Common Mistakes

Expecting every parse error in the file to be reported at once; only the first invalid line is surfaced.
Assuming a completely empty input is valid; an empty or whitespace-only file is still rejected as empty input.
Forgetting that a line containing just a scalar (e.g. "42") is valid JSONL and will appear as a bare value in the output array.

Tips

If the file is large, search for the reported line number directly in your editor rather than scrolling.
Use JSON to JSON Lines to generate valid JSONL test input for this converter.

JSON Lines to JSON Converter