Tablizer

Convert JSON to TOML Online

Paste a JSON table below, edit it if you need to, and get TOML 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 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 TOML is

TOML is a configuration format with explicit types and a table syntax, designed to be unambiguous where YAML is clever.

Rust and Python projects, and anything with a pyproject.toml or Cargo.toml.

What changes when you convert JSON to TOML

Four shapes all read correctly: an array of objects, an array of arrays with a header row, an object of column arrays, and an object keyed by row id. A single wrapper key holding the array, which is how most APIs reply, is unwrapped automatically. Nested objects are flattened one level into dotted keys; anything deeper is kept as JSON text in the cell, because a table cannot hold a tree.

Each row becomes an entry in an array of tables. Keys are sanitised to bare keys where possible and quoted where not.

What carries over from JSON to TOML

JSON records 2 things about a table that TOML has no way to hold.

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

JSON can hold a value that is itself a list or an object. TOML has only flat cells, so nested values are flattened into one cell rather than being spread across columns.

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

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

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

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 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" }
]
TOML out
[[staff]]
id = "007"
name = "Halima Yusuf"
role = "Analyst, data"
started = "2024-03-15"
hours = "38.5"

[[staff]]
id = "012"
name = "Jonah \"Jo\" Pryce"
role = "Engineer"
started = "2025-11-02"
hours = ""

[[staff]]
id = "104"
name = "Wei Chen"
role = "Manager"
started = "2023-06-30"
hours = "40"

Questions

How do I convert JSON to TOML?

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

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.

What happens to nested values?

TOML has no nested cell, so a list or object inside a JSON value is flattened into a single cell rather than expanded into extra columns. Split it before converting if the parts need to be separate.

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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