# Environment Variables
Starting from **ONEWEB version 5.0.21.01**, Page Designer introduces **Environment Variables**, a feature that allows users to **configure environment‑specific values** in a centralized and flexible way.
Environment Variables help applications adapt to different environments such as:
* **Development**
* **SIT**
* **UAT**
* **Production**
without requiring changes to page logic or redeployment of UI code.
***
### What Are Environment Variables?
**Environment Variables** are key‑value pairs that:
* Are defined per environment
* Can store configuration values (URLs, flags, identifiers, etc.)
* Can be accessed inside pages **like JavaScript variables**
They provide a clean separation between:
* **Application logic**
* **Environment‑specific configuration**
***
### Types of Environment Variables
#### User‑Defined Environment Variables
User‑defined variables allow application developers to define their own configuration values, such as:
* API base URLs
* Feature toggles
* Environment‑specific constants
* External service endpoints
Once defined, these variables can be referenced anywhere in the page application.
***
#### System‑Level Environment Variables
ONEWEB also provides **system‑level variables**, typically used for:
* **Microflow service URLs**
* **IAM2 configuration**
* Platform‑level integrations
These variables are often pre‑configured to support different runtime environments (SIT, UAT, PROD, etc.).
***
### Access Environment Variables Configuration
Environment Variables are managed from a dedicated configuration screen in Page Designer.
From this screen, users can:
* Define new variables
* Specify different values per environment
* Manage and update existing variables centrally
***
### Using Environment Variables in Pages
Once an Environment Variable is defined:
* It can be accessed within pages **like a JavaScript variable**
* It can be used inside:
* Page scripts
* Page actions
* Dynamic configurations
* Expressions and logic blocks
This allows the same page design to behave differently depending on the environment it is running in.
***
### Common Use Cases
Environment Variables are commonly used for:
* Switching API endpoints between environments
* Configuring Microflow service URLs
* Managing authentication or IAM endpoints
* Enabling or disabling environment‑specific features
* Avoiding hard‑coded configuration values
***
### Benefits of Environment Variables
Using Environment Variables provides several advantages:
* Eliminates hard‑coded URLs or constants
* Simplifies environment promotion (SIT → UAT → PROD)
* Reduces risk of configuration errors
* Improves maintainability and security
* Centralized configuration management
***
### Design Perspective
As part of **Page Designer best practices**:
* Always use Environment Variables for environment‑dependent values
* Avoid embedding environment‑specific URLs directly in pages
* Clearly name variables to reflect their purpose
* Group related variables for better readability
* Validate values when moving between environments
Environment Variables enable ONEWEB applications to remain **portable, configurable, and enterprise‑ready**.
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