YAML to TOML Converter

Convert YAML configuration to TOML format. Handles nested objects, arrays, strings, numbers.

YAML input

or drop a file here

TOML output

project = "myapp"
version = "1.0.0"
debug = false
tags = ["fast", "client-side", "open-source"]

[server]
host = "localhost"
port = 8080
ssl = true

[database]
url = "postgres://localhost/myapp"
pool = 5

YAML vs TOML — key differences

YAML and TOML are both human-readable configuration formats. TOML (Tom's Obvious Minimal Language) uses explicit [section] headers for nested objects and [[array]]for arrays of tables, making structure unambiguous. YAML uses indentation, which is flexible but can be tricky to edit manually. TOML is the default format for Rust's Cargo.toml and many modern config tools. For the reverse, try YAML Formatter or JSON to YAML.

Built and maintained by Meet Shah · Last updated 2 August 2026

What this tool is used for

Migrating configuration from a YAML tool to a TOML-based one.
Producing a TOML config for a Rust or Python project from a YAML source.
Converting a manifest for a toolchain that expects TOML.
Generating a TOML fixture from existing configuration.
Comparing a YAML config against a TOML one in the same format.

Frequently Asked Questions

How does YAML nesting become TOML?: Nested mappings become `[section]` headers with dotted paths — a `server:` block with `host` and `port` becomes `[server]` followed by those keys. TOML has no indentation semantics, so the tree is expressed by header names rather than by structure.
What is TOML strict about that YAML is not?: Quoting and typing. Every string needs quotes, so YAML's bare `localhost` becomes `"localhost"`, and TOML has no implicit conversions — which means the Norway problem, where YAML reads `no` as false, simply cannot happen. That predictability is why Cargo and pyproject.toml chose it.
How is a list of objects converted?: Into an array of tables: `[[middleware]]` repeated once per element. This is the construct people most often get wrong by hand, and it is why a YAML list of mappings cannot be converted with a simple line transformation.
What does not convert cleanly?: YAML anchors and aliases, which TOML has no equivalent for — they are resolved, so shared structure is duplicated in the output. Multi-document YAML also has no TOML counterpart, since a TOML file is exactly one document by definition.
Why does key order matter in TOML?: Because a key defined after a `[section]` header belongs to that section. Top-level keys must therefore appear before the first header, which is the one structural rule that trips people editing a converted file by hand — a key moved down a few lines silently changes table.

Common errors and gotchas

Producing deeply nested tables where TOML's syntax becomes harder to read than the YAML was.
Losing YAML's anchors and aliases, which TOML has no equivalent for and which must be expanded.
Converting a value YAML had implicitly typed, so a string becomes a TOML number or boolean.
Ordering tables incorrectly, since TOML requires a table's keys before any sub-table.
Dropping comments, which both formats support and converters routinely discard.