What is NDJSON / JSONL and how is it different from a JSON array?

NDJSON (newline-delimited JSON), also called JSONL or JSON Lines, puts one complete JSON value on each line with no commas between them and no surrounding brackets, for example a file whose lines are {"id":1} then {"id":2}. A JSON array wraps those same values in [ ] and separates them with commas. They hold the same data but only the array is a single valid JSON document; NDJSON is a sequence of documents, which is why streaming tools read it line by line.

Why would I use NDJSON instead of a normal JSON array?

NDJSON shines when data arrives or is processed one record at a time. Log shippers append a line per event, a streaming endpoint can flush a line as soon as a row is ready, and a reader can stop at any line without parsing the whole file. A 5 GB array forces you to load the entire thing before the first object is usable; the same data as NDJSON is processed line by line with near-zero memory. That is why logs, exports and message queues prefer it.

Which tools and services consume NDJSON?

BigQuery bulk loads expect newline-delimited JSON, the Elasticsearch and OpenSearch _bulk API speaks NDJSON, jq emits it by default, pandas read_json supports lines=True, and many HTTP streaming APIs send NDJSON responses. If a service tells you to upload JSONL or one JSON object per line, this is the format. Convert your array here, paste the NDJSON into the import dialog, and the row-per-line shape lines up with what the loader parses.

A line failed to parse. How do I find which one?

When you convert NDJSON to a JSON array, the tool parses each line on its own and stops at the first one that fails, showing the 1-based line number, for example Line 3 with the parser message. Blank lines that are skipped still count toward that number, so the line you see matches your editor. A common cause is a trailing comma left over from copying out of a JSON array, since each NDJSON line must be a standalone value with no comma.

Is this safe for large files and private data?

Yes on both counts. The conversion is plain JavaScript that runs in your browser tab, so nothing you paste is uploaded or logged anywhere. Because NDJSON is line oriented, big inputs convert quickly without building a huge intermediate structure. The one caveat is the share link: your input is stored in the URL so a pasted link reproduces the conversion, which means very large or confidential data should be moved with the copy button rather than a shared URL.

Prepare a BigQuery bulk load

You exported a table as a JSON array but BigQuery's load job only accepts newline-delimited JSON. Paste the array, switch to array to NDJSON, and you get one object per line ready to drop into the load UI or pipe into bq load with --source_format=NEWLINE_DELIMITED_JSON. No script, no jq one-liner to remember.

Build an Elasticsearch _bulk payload base

The _bulk API wants one JSON document per line. Convert your array of source documents to NDJSON here to get the row-per-line shape, then interleave the action lines your indexer needs. Starting from clean NDJSON beats hand-splitting an array and hoping every comma landed in the right place.

Inspect a streaming log dump as a real array

A service handed you a .ndjson log file and you want to eyeball it as structured data. Paste the lines, convert NDJSON to a JSON array at 2-space indent, and now you can fold it, search it, or drop it into a JSON viewer. If a line is malformed, the tool points you straight at the line number instead of failing silently.

Fix the one broken row in a 100k-line export

A nightly export of 100,000 NDJSON lines fails to import and you have no idea which row is bad. Paste it, convert to array, and the tool stops at the first unparseable line with its number, for example Line 83,402. You fix that single row and re-run the import instead of bisecting the file by hand.

JSON to NDJSON Converter (and NDJSON to JSON)

JSON array to NDJSON and back, one compact JSON value per line, with bad-line numbers and pick-your-indent, all in your browser

Runs locally
Category Format Converter
Best for Turning pasted content or local files into a handoff-friendly format.

Direction

Input

Output

What this tool does

A free two-way converter between a JSON array and NDJSON, the newline-delimited JSON format also written JSONL or JSON Lines. Going array to NDJSON, the tool parses your [{...},{...}] array and writes every element as one compact JSON value on its own line, which is the exact shape that streaming pipelines, append-only log files and bulk loaders expect. Going the other way, it reads one JSON value per line, collects them into a single array and pretty-prints it at compact, 2-space or 4-space indent. Blank lines can be skipped, and when a line will not parse the tool gives you its 1-based line number so you can jump straight to the broken row in a million-line file. It counts lines and objects, copies the result with one click, and keeps your input and direction in the URL so a share link reopens the same conversion. Everything runs locally in your browser tab. No upload, no server, no log of what you paste.

Tool details

Input: Files + Text + Structured content; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 9 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Format Converter · Developer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How JSON to NDJSON Converter fits into your work

Use it when the main problem is getting content from one practical format into another.

Conversion jobs

Turning pasted content or local files into a handoff-friendly format.
Previewing a conversion before you use it in a larger workflow.
Cleaning small format mismatches without opening a full editor.

Conversion checks

Try a small sample first when the source format is messy.
Check character encoding, separators, and line endings after conversion.
Keep the source until the converted output has been reviewed.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Prepare a BigQuery bulk load
You exported a table as a JSON array but BigQuery's load job only accepts newline-delimited JSON. Paste the array, switch to array to NDJSON, and you get one object per line ready to drop into the load UI or pipe into bq load with --source_format=NEWLINE_DELIMITED_JSON. No script, no jq one-liner to remember.
Build an Elasticsearch _bulk payload base
The _bulk API wants one JSON document per line. Convert your array of source documents to NDJSON here to get the row-per-line shape, then interleave the action lines your indexer needs. Starting from clean NDJSON beats hand-splitting an array and hoping every comma landed in the right place.
Inspect a streaming log dump as a real array
A service handed you a .ndjson log file and you want to eyeball it as structured data. Paste the lines, convert NDJSON to a JSON array at 2-space indent, and now you can fold it, search it, or drop it into a JSON viewer. If a line is malformed, the tool points you straight at the line number instead of failing silently.
Fix the one broken row in a 100k-line export
A nightly export of 100,000 NDJSON lines fails to import and you have no idea which row is bad. Paste it, convert to array, and the tool stops at the first unparseable line with its number, for example Line 83,402. You fix that single row and re-run the import instead of bisecting the file by hand.

Common pitfalls

Feeding a single JSON object instead of an array when going array to NDJSON. The mapping is one array element to one line, so the input must be wrapped in [ ]. A lone {"a":1} is rejected; write [{"a":1}] if you really have one record.
Leaving trailing commas on NDJSON lines after copying out of an array. Each line must be a standalone JSON value, so {"a":1}, with a comma fails to parse. Convert the whole array here instead of editing lines by hand.
Expecting the NDJSON output to be a single valid JSON document. It is not; it is a sequence of values with no outer brackets, so do not paste raw NDJSON into a tool that wants one JSON object. Convert back to an array first when you need a single document.

Privacy

Every step here, the array-to-NDJSON split and the NDJSON-to-array join, is plain JavaScript running in your browser tab. Nothing you paste is uploaded, and there is no log of your data anywhere. The one caveat: the shareable link encodes your input and direction in the URL, so a link pasted into chat records that data in the recipient server's access log. For confidential payloads, use the copy button and paste the text rather than sharing the URL.

FAQ

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Developer

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JSON to NDJSON Converter (and NDJSON to JSON)

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How JSON to NDJSON Converter fits into your work

Conversion jobs

Conversion checks

Good next steps

Real-world use cases

Prepare a BigQuery bulk load

Build an Elasticsearch _bulk payload base

Inspect a streaming log dump as a real array

Fix the one broken row in a 100k-line export

Common pitfalls

Privacy

FAQ

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