Crate config

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Config organizes hierarchical or layered configurations for Rust applications.

Config lets you set a set of default parameters and then extend them via merging in configuration from a variety of sources:

  • Environment variables
  • String literals in well-known formats
  • Another Config instance
  • Files: TOML, JSON, YAML, INI, RON, JSON5 and custom ones defined with Format trait
  • Manual, programmatic override (via a .set method on the Config instance)

Additionally, Config supports:

  • Live watching and re-reading of configuration files
  • Deep access into the merged configuration via a path syntax
  • Deserialization via serde of the configuration or any subset defined via a path

See the examples for general usage information.




  • A prioritized configuration repository. It maintains a set of configuration sources, fetches values to populate those, and provides them according to the source’s priority.
  • A configuration source backed up by a file.
  • Describes a file sourced from a file
  • Describes a file sourced from a string
  • A configuration value.


  • Represents all possible errors that can occur when working with configuration.
  • File formats provided by the library.
  • Underlying kind of the configuration value.


  • Describes a generic source of configuration properties capable of using an async runtime.
  • An extension of Format trait.
  • Describes a format of configuration source data
  • Describes a generic source of configuration properties.

Type Aliases