Tablizer

Convert JSON Lines to JSON Online

Paste a JSON Lines table below, edit it if you need to, and get JSON back. The conversion runs in your browser, so nothing is uploaded, there is no size limit and there is no signup.

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What JSON Lines is

JSON Lines is one complete JSON object per line, with no enclosing array and no commas between records. The file is not valid JSON as a whole, and that is the point.

Log pipelines, machine learning datasets and anything that appends records or reads them in a stream.

What JSON is

JSON is a text format for nested data: objects with named keys, arrays, strings, numbers, booleans and null. It has no date type and no comments.

Every web API, most configuration files and anything that talks to JavaScript.

What changes when you convert JSON Lines to JSON

Each line is parsed on its own, so a corrupt record does not take the file with it. Keys are unioned across lines in first-seen order, so a record missing a field leaves that cell empty rather than shifting the columns.

You choose the shape. An array of objects is the default and the one most code expects. A 2D array is smaller. Column arrays suit charting libraries. A keyed object suits lookups by id.

What carries over from JSON Lines to JSON

One property of the JSON Lines has no home in JSON, and it is worth knowing which before you convert.

JSON Lines can be read one record at a time. JSON has to be complete before it means anything, so the whole table is held in memory while it is written and a file that gets cut off part way through is not partly usable - it is unusable.

Both formats record types, so numbers, booleans and nulls survive as themselves rather than as text.

The identifier 007 comes out of the JSON as 007. Reading it as a number would have made it 7, and an id that changes value is worse than one that stays text.

The role "Analyst, data" survives with its comma, in one cell rather than split across two. That is the first thing to check in any converted table, and the usual place a JSON file goes wrong.

The quotes around Jonah "Jo" Pryce are escaped with a backslash in the JSON.

A worked example

Three rows of staff data, with an identifier that has a leading zero, a value containing a comma, a value containing quotes and one blank cell. Those are the four places formats disagree, so they are the four places to look.

JSON Lines in
{"id":"007","name":"Halima Yusuf","role":"Analyst, data","started":"2024-03-15","hours":"38.5"}
{"id":"012","name":"Jonah \"Jo\" Pryce","role":"Engineer","started":"2025-11-02","hours":""}
{"id":"104","name":"Wei Chen","role":"Manager","started":"2023-06-30","hours":"40"}
JSON out
{
  "staff": [
    {
      "id": "007",
      "name": "Halima Yusuf",
      "role": "Analyst, data",
      "started": "2024-03-15",
      "hours": "38.5"
    },
    {
      "id": "012",
      "name": "Jonah \"Jo\" Pryce",
      "role": "Engineer",
      "started": "2025-11-02",
      "hours": ""
    },
    {
      "id": "104",
      "name": "Wei Chen",
      "role": "Manager",
      "started": "2023-06-30",
      "hours": "40"
    }
  ]
}

Questions

How do I convert JSON Lines to JSON?

Paste your JSON Lines into the box above or drop the file onto it. Check the table in the grid, then copy or download the JSON from the output panel. It takes one step and the data never leaves your browser.

What is the difference between JSON and JSON Lines?

JSON wraps records in an array, so a reader must load the whole document before it can use any of it, and appending means rewriting the file. JSON Lines has no wrapper, so records can be streamed and appended one at a time. Use JSON for a payload, JSON Lines for a log.

Why did my zip code lose its leading zero?

Type inference turned the text 07030 into the number 7030. Tablizer leaves inference off by default for exactly this reason, and refuses to convert any value starting with a zero followed by a digit even when it is on.

Is there a limit on file size?

No. The work happens on your own machine, so the limit is your machine's memory rather than an upload cap. A file with tens of thousands of rows converts in a second or two.

Is my data uploaded anywhere?

No. The parsing and generating are done by JavaScript running on this page. You can watch the network tab while you convert and see that nothing is sent.

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