Convert CSV to TOML Online

Paste a CSV 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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Nothing here is uploaded. The parsing happens on this page.

Edit

Paste or upload something above and it will appear here.

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Header rowDetect numbers

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

What CSV is

CSV is a text file where each line is a row and commas separate the fields. There is no type system, no formatting and no second sheet. Every value is text until something downstream decides otherwise.

Almost every database, analytics tool and spreadsheet can read and write it, which is why exports default to it.

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 CSV to TOML

Reading CSV means deciding three things the file does not state: which character separates fields, how quotes work, and what encoding the bytes are in. Tablizer sniffs the delimiter from the first few lines, handles quoted fields containing commas and newlines, and reads the file as UTF-8.

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 CSV to TOML

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

TOML wants a type for each column, and CSV 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.

TOML 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.

CSV can be read one record at a time. TOML 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 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.

CSV in

id,name,role,started,hours
007,Halima Yusuf,"Analyst, data",2024-03-15,38.5
012,"Jonah ""Jo"" Pryce",Engineer,2025-11-02,
104,Wei Chen,Manager,2023-06-30,40

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 CSV to TOML?

Paste your CSV 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 does my CSV open with all the data in one column?

The file uses a delimiter your spreadsheet did not expect. Exports from European locales often use semicolons because the comma is the decimal separator there. Change the delimiter in the export options and the columns split correctly.

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.