How to Convert YAML to TOML

Problem

Your tool expects TOML configuration but your config is written in YAML.

Prerequisites

• Understanding of YAML
• Understanding of TOML structure

Steps

1. 1. Parse the YAML

   Read and parse the YAML file into an in-memory object. YAML supports nested maps, sequences, and scalars. Ensure the YAML is valid before conversion.

   Input

   server:\n  port: 8080\n  host: localhost

   Output

   parsed object

2. 2. Convert to TOML structure

   TOML uses [table] headers for nested objects and key = value for scalars. Arrays of tables use [[table]]. Convert YAML maps to TOML tables, sequences to TOML arrays, and scalars to TOML values. TOML does not support null; decide how to handle null values.

   Input

   server.port: 8080

   Output

   [server]\nport = 8080

3. 3. Serialize and validate

   Write the TOML output and parse it back to verify correctness. Check that types are preserved (strings, integers, booleans, dates). TOML has native datetime support, which YAML also supports, but the format differs.

   Input

   TOML output

   Output

   round-trip valid

Expected result

A valid TOML file equivalent to the original YAML configuration.

Common errors

YAML null has no TOML equivalent

TOML does not support null values. Omit the key, use a sentinel value, or switch to a format that supports null.

Mixed types in arrays

TOML arrays must contain homogeneous types. YAML allows mixed-type arrays. Ensure your YAML arrays are type-consistent before converting.

Troubleshooting

• If TOML parsing fails, check for unsupported types or syntax.
• TOML keys must be bare strings; quote keys with special characters.

Security limits

• TOML is safer to parse than YAML because it does not support executable tags. However, always use a trusted parser.