config.json: A concise guide to application configuration

What is config.json

config.json is a JSON file used by many software projects to store configuration data. It typically holds non-secret settings like UI options, feature flags, endpoints, logging levels, and environment-specific values. JSON is lightweight and language-agnostic, making config.json a portable choice across stacks.

Common uses

In standalone apps

config.json is often read at startup to customize behavior without hard-coding values. It can store endpoints, feature flags, or UI preferences.

In containerized or cloud deployments

config.json can be mounted as a volume or injected with environment-specific values. Some projects support multiple configs per environment (for example, config.dev.json or config.prod.json) or merging with environment variables.

Key features

JSON syntax

JSON stores data as key-value pairs, arrays, and nested objects. It is human-readable, but standard JSON does not support comments (some parsers allow them).

Typical fields

A typical config.json might include fields like:

• name: my-app
• version: 1.0.0
• endpoint: https://api.example.com
• settings:
• theme: dark
• itemsPerPage: 20
• logging:
• level: info

Practical example (non-quoted)

The following illustrates a simple structure in plain text (for readability) rather than strict JSON:

name: my-app version: 1.0.0 endpoint: https://api.example.com settings: theme: dark itemsPerPage: 20 logging: level: info

Best practices

Validation and schema

Consider using a JSON Schema or similar validation to catch misconfig at startup.

Handling secrets and environment-specific values

Avoid storing secrets in config.json. Use environment variables, secret managers, or encrypted files. Maintain separate configs per environment and merge them at runtime.

Version control and deployment

Track config changes in version control, but exclude secrets. Provide a sample configuration file (config.example.json) that illustrates defaults.