What is the difference between INI, TOML, and .env files?

INI files have sections and key-value pairs but no type system. TOML adds explicit types, arrays, inline tables, and strict parsing rules, making it better for complex configs. .env files have no sections and are simple KEY=VALUE pairs for environment variable injection.

What is a .properties file?

A .properties file is a Java convention similar to INI with no sections — just key=value pairs with # comments. It is used extensively in Java applications, Spring Boot, and Android for i18n resource bundles. Unlike INI, there is no concept of sections.

Should I still use INI for new projects?

For new projects, prefer TOML (if you need sections and types) or YAML (if the tooling requires it). INI is fine for simple legacy systems and tools that already use it, but the lack of a standard and type system make it less suitable for complex modern applications.

What is the difference between INI, TOML, and .env files?

INI files have sections and key-value pairs but no type system. TOML adds explicit types, arrays, inline tables, and strict parsing rules, making it better for complex configs. .env files have no sections and are simple KEY=VALUE pairs for environment variable injection.

What is a .properties file?

A .properties file is a Java convention similar to INI with no sections — just key=value pairs with # comments. It is used extensively in Java applications, Spring Boot, and Android for i18n resource bundles. Unlike INI, there is no concept of sections.

Should I still use INI for new projects?

For new projects, prefer TOML (if you need sections and types) or YAML (if the tooling requires it). INI is fine for simple legacy systems and tools that already use it, but the lack of a standard and type system make it less suitable for complex modern applications.

What is an INI File? — Configuration File Format Explained

Definition

An INI file is a simple configuration file format originally from early Windows software that organizes settings as key-value pairs grouped under named sections. The format is human-readable and easy to edit manually. INI files have no formal specification, leading to slight variations between implementations, but the basic structure of [section], key = value, and # or ; comments is universally understood. INI format is used in Windows configuration files, PHP's php.ini, Git's .gitconfig, Python's configparser, and many other tools.

How It Works

An INI file consists of sections (names in square brackets like [database]) and key-value pairs under each section (key = value). Keys and values are separated by = or :. Comments start with # or ;. Sections group related settings and allow the same key name to appear in different sections with different values. There is no support for nested structures, arrays, or data types beyond strings — all values are plain text that applications parse themselves. The global section (before any section header) is supported by some parsers.

Common Use Cases

▸PHP configuration in php.ini for settings like memory_limit and upload_max_filesize
▸Git configuration in ~/.gitconfig for user name, email, and aliases
▸Windows registry-like configuration for legacy Windows applications
▸Python configparser-based application configuration
▸Database connection settings in Django's legacy my.cnf-style configs

Example

[server]
host = localhost
port = 8080
debug = true

[database]
host = db.example.com
port = 5432
name = myapp
user = appuser
password = secret

[logging]
level = INFO
file = /var/log/app.log

Related Tools

INIINI File Formatter

Format INI and .properties files with consistent spacing and section headers.

≡Properties Formatter

Format and sort Java .properties files with aligned equals signs.

FAQ

What is the difference between INI, TOML, and .env files?: INI files have sections and key-value pairs but no type system. TOML adds explicit types, arrays, inline tables, and strict parsing rules, making it better for complex configs. .env files have no sections and are simple KEY=VALUE pairs for environment variable injection.
What is a .properties file?: A .properties file is a Java convention similar to INI with no sections — just key=value pairs with # comments. It is used extensively in Java applications, Spring Boot, and Android for i18n resource bundles. Unlike INI, there is no concept of sections.
Should I still use INI for new projects?: For new projects, prefer TOML (if you need sections and types) or YAML (if the tooling requires it). INI is fine for simple legacy systems and tools that already use it, but the lack of a standard and type system make it less suitable for complex modern applications.

Related Terms

TOML YAML JSON