Convert HTML to Protobuf Schema Online

Paste a HTML table below, edit it if you need to, and get Protobuf Schema 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 numbers

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 Protobuf Schema is

A proto3 message definition with numbered fields.

gRPC services and anything using Protocol Buffers.

What changes when you convert HTML to Protobuf Schema

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.

Field numbers are assigned in column order starting at one. Types are inferred from the values.

What carries over from HTML to Protobuf Schema

HTML records 2 things about a table that Protocol Buffers has no way to hold.

Protocol Buffers 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.

Protocol Buffers 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 Protocol Buffers 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 Protocol Buffers file that is cut off part way through still gives you every record before the cut.

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>

Protobuf Schema out

syntax = "proto3";

message staff {
  int64 id = 1;
  string name = 2;
  string role = 3;
  string started = 4;
  double hours = 5;
}

Questions

How do I convert HTML to Protobuf Schema?

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

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.