Convert JSON to TOML from an object, then review every null value before you use the output. FindUtils JSON TOML Converter writes nested objects as tables and reports the null values that it removes or replaces.
The tool supports conversion in both directions. This guide explains the available settings, a repeatable example, and information that a conversion cannot preserve.
Why does JSON to TOML need a null rule?
TOML 1.0 supports strings, numbers, booleans, date and time values, arrays, and tables. It has no null type. A converter must therefore reject a JSON null or apply a replacement rule. See the TOML 1.0 specification.
FindUtils offers two rules: Drop removes the null value; Empty string replaces it with "". Neither rule preserves null as null.
- Optional settings: Removing a key can activate a destination default.
- Text fields: An empty string can mean an intentionally blank value.
- Arrays: Removing an entry changes the array length and later indexes.
These differences matter even when the resulting TOML is valid. Choose the rule from the receiving application's requirements.
How to convert JSON to TOML
Use a small object with one null value first. Check the complete result before you convert a larger document.
Step 1: Select the conversion direction
Open the JSON TOML Converter. Select JSON to TOML. Paste this invented configuration example. The root is an object, as this converter requires.
{
"app": {
"name": "Field Notes",
"enabled": true,
"ports": [8080, 8081],
"description": null
},
"targets": [
{"name": "preview", "enabled": true},
{"name": "release", "enabled": false}
]
}Step 2: Select a null policy
Leave Nulls set to Drop for the first comparison. The output omits app.description. The Notes area names that path. Confirm that an absent description is acceptable.
Step 3: Check the tables and arrays
The app object becomes a table. Its numeric array stays inline. Each object inside targets becomes a separate array-of-tables entry. The output has this structure:
[app] name = "Field Notes" enabled = true ports = [ 8080, 8081 ] [[targets]] name = "preview" enabled = true [[targets]] name = "release" enabled = false
Step 4: Compare the empty-string option
Select Empty string. The app table now includes description = "". The notes still identify app.description. Keep this setting only if the destination expects an empty string.
Step 5: Export the reviewed result
Copy the TOML or download converted.toml. Select TOML to JSON if you want to inspect the converted values as JSON. The current output moves into the input when you switch direction.
Examples that need a separate decision
Nulls, dates, and package metadata need more than a syntax check. The following examples identify what the converter can produce and what you must decide.
A null inside an array
For {"stages":["draft",null,"approved"]}, Drop produces an array with two entries. approved moves from index 2 to index 1. Empty string keeps three entries but changes the middle value to a string.
The notes identify stages[1] in either case. Do not accept the shorter array if another setting refers to an entry by position. Change the source representation if neither option matches the destination's requirements.
A date that changes type
A JSON date string stays a quoted TOML string. The converter does not decide that a date-shaped string should become a TOML date.
{"release_date": "2026-09-08"}release_date = "2026-09-08"
An unquoted TOML local date follows another path:
release_date = 2026-09-08
The JSON result contains "release_date": "2026-09-08". JSON has no native date type, so that output cannot record whether the source used a TOML date or a string.
Converting that JSON back produces a quoted TOML string. A successful conversion in both directions therefore does not prove that every type survived.
A generated project file
The converter can serialize an object that already has the required tables for a destination file. It does not translate one application's settings into another application's schema.
For example, a JSON property named dependencies does not tell the converter how a particular package tool expects versions or optional features. Check those requirements separately. Valid TOML alone does not establish that a project file is valid for its consumer.
What survives the conversion?
Use this table as a review plan. It compares representations rather than claiming that the formats are interchangeable.
| Source value or feature | Converter result | Required check |
|---|---|---|
| JSON object | TOML table structure | Table names match the destination |
| JSON array of objects | TOML array of tables | Entry order and count remain correct |
| JSON scalar array | TOML inline array | Values and their types match |
| JSON null | Removed value or empty string | The replacement has the intended meaning |
| JSON date string | Quoted TOML string | The consumer accepts a string |
| TOML date or time | JSON string representation | Native date or time type information is lost |
| TOML comment | No JSON comment | Keep explanations in the original document |
Sort keys sorts object keys at each level for JSON-to-TOML output. It does not sort array entries. Sorting can make files easier to compare, but it cannot correct an incorrect value.
Common mistakes and corrections
Check the source structure before you investigate a parser error. Some valid JSON values are outside this converter's accepted input shape.
Mistake 1: Starting with a root array
The JSON root must be an object. A bare array produces a root error. Place it under a meaningful property only if the receiving application expects that property.
Mistake 2: Treating removed nulls as harmless
Read the notes before you copy the output. Inspect each named path. Removal can affect defaults, required fields, or array positions.
Mistake 3: Expecting comments to return
TOML comments do not enter the JSON result. A later conversion cannot reconstruct them. Keep the original file as the record of human explanations.
Mistake 4: Treating dates as ordinary text in both directions
Check whether the source date has quotes. A date-shaped string and a native TOML date can produce the same JSON string. Record the original type when it matters to the destination.
Mistake 5: Ignoring number precision
JSON parsing in this browser tool uses JavaScript numbers. Very large integer values can lose precision before TOML output. Keep exact identifiers as strings. The JSON standard's number guidance explains interoperability limits.
Tools used in this guide
FindUtils provides separate tools for the source format and the review task.
- JSON TOML Converter converts JSON objects and TOML documents in the browser.
- JSON Formatter checks JSON syntax and makes nested data easier to read.
- Properties JSON Converter handles Java properties when that is the actual source format.
FAQ
Q1: Does TOML support null? A: No. The converter offers removal or an empty string. Both options change the original JSON value.
Q2: Does sorting change the order of array entries? A: No. This converter sorts object keys. It keeps array entry order, except that the Drop policy removes null entries.
Q3: Can I convert TOML back to JSON? A: Yes. Select TOML to JSON. The output uses JSON-compatible values and string representations for date and time values.
Q4: Does this tool validate a package manifest? A: No. It converts the document syntax and data structure. It does not check application-specific manifest requirements.
Q5: Does the converter upload the document? A: Conversion runs in the browser without sending the document to FindUtils. The page can still load advertisements and other external resources.
Q6: Can I use this converter through REST or MCP? A: No. This converter currently has a browser page only. The page does not require an account.
Next steps
Use the configuration conversion review before you replace an existing file. Read the ENV to JSON guide for flat environment values. Read the Properties to JSON guide for dotted property names and Java escapes.
