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Rust Build Status

Layered configuration system for Rust applications (with strong support for 12-factor applications).

  • Set defaults
  • Set explicit values (to programmatically override)
  • Read from JSON, TOML, YAML, INI, RON, JSON5 files
  • Read from environment
  • Loosely typed — Configuration values may be read in any supported type, as long as there exists a reasonable conversion
  • Access nested fields using a formatted path — Uses a subset of JSONPath; currently supports the child ( redis.port ) and subscript operators ( databases[0].name )

Please note this library

  • can not be used to write changed configuration values back to the configuration file(s)!
  • Is case insensitive and all the keys are converted to lowercase internally


config = "0.14.0"

Feature flags

  • ini - Adds support for reading INI files
  • json - Adds support for reading JSON files
  • yaml - Adds support for reading YAML files
  • toml - Adds support for reading TOML files
  • ron - Adds support for reading RON files
  • json5 - Adds support for reading JSON5 files

Support for custom formats

Library provides out of the box support for most renowned data formats such as JSON or Yaml. Nonetheless, it contains an extensibility point - a Format trait that, once implemented, allows seamless integration with library's APIs using custom, less popular or proprietary data formats.

See custom_file_format example for more information.


See the documentation or examples for more usage information.


We currently support Rust 1.75.0 and newer.


config-rs is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0).