envfile

An envfile is a plain text file that stores environment variables in a key=value format and is used to configure software applications at runtime. It is commonly named .env or envfile and is read by applications or by shell scripts during startup. The concept is widely used across programming languages and deployment environments, though there is no single formal standard. Many frameworks provide libraries to parse such files and inject the variables into the process environment.

Format and syntax typically involve lines that define a variable as KEY=value. Non-empty lines that do not start with a comment character are treated as definitions. Leading and trailing whitespace is usually ignored. Lines starting with # are comments. Values may be unquoted or quoted; quotes may be preserved or stripped depending on the parser. Some implementations support escaping, an export form (export KEY=value), or multi-line values with backslashes. Different tools may have small variations in rules, so a project’s documentation should be consulted for specifics.

Usage and best practices include using envfiles to separate configuration from code and loading them at application startup. It is important not to commit sensitive data to version control; add envfiles to ignore lists and consider per-environment files. In production, secure secrets management is preferred, and envfiles are typically used for local development, testing, or staging rather than as a sole security mechanism.

Limitations include lack of encryption and the potential exposure of credentials if files are mishandled. Cross-platform parsing differences can exist, and some values may require escaping for particular shells. When deploying, ensure the runtime environment can read the file and that overrides are applied as needed.