Convert HTML to JSON Lines Online

Paste a HTML table below, edit it if you need to, and get JSON Lines 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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Nothing here is uploaded. The parsing happens on this page.

Edit

Paste or upload something above and it will appear here.

ToDataMarkupDocumentsCodeSchemasImages

Header rowDetect numbersShapeIndentEmpty cells

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

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 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 changes when you convert HTML to JSON Lines

The first table in the markup is used. Cell contents are stripped of inline tags and entities are decoded, so <td><b>Total</b> </td> arrives as Total. Nested tables inside a cell are not descended into.

Every row becomes one line. You can append to the file forever without rewriting it, and a reader can process it a line at a time without holding the whole thing in memory.

What carries over from HTML to JSON Lines

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

JSON Lines wants a type for each column, and HTML does not record one, so each column is typed from what its values look like. A column of digits that should stay text - a zip code, a phone number, a leading-zero id - is the usual thing to check afterwards.

A line break inside a cell ends the row in JSON Lines, so line breaks are replaced rather than carried through.

JSON Lines has no header row. The column names are repeated as keys on every record instead, which is why the result is bigger on disk than the table it came from.

Anything visual in the HTML - weight, alignment, colour, column widths - has no counterpart in JSON Lines and is dropped. The values are what survives.

The result can be read a record at a time, and appended to by adding to the end of it. That is worth having for a table too large to hold in memory, and it means a JSON Lines file that is cut off part way through still gives you every record before the cut.

The identifier 007 comes out of the JSON Lines 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 Lines file goes wrong.

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

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.

HTML in

<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 "Jo" 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>

JSON Lines out

{"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 HTML to JSON Lines?

Paste your HTML into the box above or drop the file onto it. Check the table in the grid, then copy or download the JSON Lines 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.

One of my cells has a line break in it - what happens?

A line break would end the row in JSON Lines, so it is replaced instead of carried through. The rest of the cell stays where it belongs.

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.