TOML

Tom's Obvious, Minimal Language.

By Tom Preston-Werner, Pradyun Gedam, et al.

This repository contains the in-development version of the TOML specification. You can find the released versions at https://toml.io.

Objectives

TOML aims to be a minimal configuration file format that's easy to read due to obvious semantics. TOML is designed to map unambiguously to a hash table. TOML should be easy to parse into data structures in a wide variety of languages.

Example

# This is a TOML document.

title = "TOML Example"

[owner]
name = "Tom Preston-Werner"
dob = 1979-05-27T07:32:00-08:00 # First class dates

[database]
server = "192.168.1.1"
ports = [ 8000, 8001, 8002 ]
connection_max = 5000
enabled = true

[servers]

  # Indentation (tabs and/or spaces) is allowed but not required
  [servers.alpha]
  ip = "10.0.0.1"
  dc = "eqdc10"

  [servers.beta]
  ip = "10.0.0.2"
  dc = "eqdc10"

[clients]
data = [ ["gamma", "delta"], [1, 2] ]

# Line breaks are OK when inside arrays
hosts = [
  "alpha",
  "omega"
]

Comparison with Other Formats

TOML shares traits with other file formats used for application configuration and data serialization, such as YAML and JSON. TOML and JSON both are simple and use ubiquitous data types, making them easy to code for or parse with machines. TOML and YAML both emphasize human readability features, like comments that make it easier to understand the purpose of a given line. TOML differs in combining these, allowing comments (unlike JSON) but preserving simplicity (unlike YAML).

Because TOML is explicitly intended as a configuration file format, parsing it is easy, but it is not intended for serializing arbitrary data structures. TOML always has a hash table at the top level of the file, which can easily have data nested inside its keys, but it doesn't permit top-level arrays or floats, so it cannot directly serialize some data. There is also no standard identifying the start or end of a TOML file, which can complicate sending it through a stream. These details must be negotiated on the application layer.

INI files are frequently compared to TOML for their similarities in syntax and use as configuration files. However, there is no standardized format for INI and they do not gracefully handle more than one or two levels of nesting.