Convert JSON Lines to HTML Online

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

From

From a page

The only part of this site that uses a server. The address is sent to it so the page can be fetched, because a browser is not allowed to fetch someone else's page itself. Your own files are never involved.

Nothing here is uploaded. The parsing happens on this page.

Edit

Paste or upload something above and it will appear here.

ToDataMarkupDocumentsCodeSchemasImages

Header rowDetect numbersclassWrap in a div

The output will appear here once there is a table to convert.

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 HTML is

An HTML table is a table element containing thead and tbody, with th cells for headers and td cells for data.

Web pages, email templates and anything pasted into a CMS.

What changes when you convert JSON Lines to HTML

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.

Semantic markup: a real thead, a real tbody, th for the header row. Angle brackets and ampersands in your data are escaped, so a value like <script> is written safely and shows as text on the page.

What carries over from JSON Lines to HTML

JSON Lines records 3 things about a table that HTML has no way to hold.

JSON Lines distinguishes a number from the text of a number; HTML does not, so every value arrives as text and has to be re-parsed by whatever reads it next.

An empty cell and a missing one are the same thing in HTML, so a null and an empty string in the JSON Lines both come out blank and can no longer be told apart.

HTML marks header cells differently from data cells, so the keys are lifted out and written once as a marked header row rather than repeated on every row.

JSON Lines can be read one record at a time. HTML 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.

The identifier 007 comes out of the HTML 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 HTML file goes wrong.

The quotes around Jonah "Jo" Pryce are written as the HTML entity " in the HTML.

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"}

HTML out

<table>
  <thead>
    <tr>
      <th>id</th>
      <th>name</th>
      <th>role</th>
      <th>started</th>
      <th>hours</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>007</td>
      <td>Halima Yusuf</td>
      <td>Analyst, data</td>
      <td>2024-03-15</td>
      <td>38.5</td>
    </tr>
    <tr>
      <td>012</td>
      <td>Jonah &quot;Jo&quot; Pryce</td>
      <td>Engineer</td>
      <td>2025-11-02</td>
      <td></td>
    </tr>
    <tr>
      <td>104</td>
      <td>Wei Chen</td>
      <td>Manager</td>
      <td>2023-06-30</td>
      <td>40</td>
    </tr>
  </tbody>
</table>

Questions

How do I convert JSON Lines to HTML?

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 HTML 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.

Will my numbers still be numbers?

They will read the same, but HTML stores them as text. Anything that sorts or sums the result will need to parse them first, and a leading zero or a currency symbol is the usual place that goes wrong.

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.