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 Firebase is
JSON shaped for a Realtime Database import: an object keyed by record id rather than an array.
Firebase projects.
What changes when you convert HTML to Firebase
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.
Keys come from the first column. Firebase does not store arrays natively, so a keyed object is the correct shape for an import.
What carries over from HTML to Firebase
HTML records 2 things about a table that Firebase has no way to hold.
Firebase 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.
Firebase 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 Firebase and is dropped. The values are what survives.
The identifier 007 comes out of the Firebase 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 Firebase file goes wrong.
The quotes around Jonah "Jo" Pryce are escaped with a backslash in the Firebase.