JSON to TOML Converter: Config File Guide (and Why Numbers Look Like 3_000)

TOML (Tom’s Obvious Minimal Language) is widely used for configuration:

• Rust tooling (Cargo.toml)
• Static site generators
• CI and developer tools

If your data starts as JSON (API output, app configs, generated settings), it’s often useful to convert it into TOML.

Use our JSON to TOML converter to generate a clean TOML config instantly.

Quick example: JSON → TOML

JSON input

json{
  "app": {
    "name": "demo-web",
    "env": "production",
    "port": 8080,
    "features": ["markdown_export", "xml_import"]
  },
  "database": {
    "host": "localhost",
    "port": 5432,
    "user": "demo",
    "ssl": false
  }
}

TOML output

toml[app]
name = "demo-web"
env = "production"
port = 8_080
features = ["markdown_export", "xml_import"]

[database]
host = "localhost"
port = 5_432
user = "demo"
ssl = false

Why does TOML sometimes format numbers like 3_000?

TOML allows underscores in numbers as visual separators.

• 3000 and 3_000 are the same value
• It’s similar to numeric separators in many programming languages

So if you see 8_080 or 5_000, that’s valid TOML and will parse correctly.

Step-by-step: how to convert JSON to TOML

1. Open JSON to TOML
2. Paste JSON input (or click Sample)
3. Copy or download the TOML output

How JSON maps to TOML

Objects → Tables

json{ "app": { "name": "demo" } }

becomes:

toml[app]
name = "demo"

Nested objects → Dotted tables

json{ "app": { "features": { "beta": true } } }

becomes:

toml[app.features]
beta = true

Arrays → Arrays

json{ "features": ["a", "b"] }

becomes:

tomlfeatures = ["a", "b"]

Convert back when needed

If you need JSON again (for APIs or scripts), use TOML to JSON.

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Try it now

• Convert JSON to TOML: JSON to TOML
• Convert TOML to JSON: TOML to JSON