---
area: "Learn"
parent: "Getting started chapter"
url: "https://unpoly.com/learn/start/api"
---
# The shape of the API
Most of Unpoly's features share one shape: the common case is an HTML attribute, the same feature is also available as a JavaScript function, and its defaults can be changed through a global configuration. Learn the pattern once, and every feature in the reference will look familiar.
## Every attribute has a JavaScript counterpart {#javascript-counterparts}
The quickest way is an attribute in your HTML. This link swaps the [main fragment](https://unpoly.com/api/main.md) with an animated transition:
```html
Click me
```
The same feature exists as a JavaScript function, for when your own code triggers the behavior. Attributes become camel-cased options:
```js
up.follow(link, { transition: 'cross-fade' })
```
When your whole app should behave that way, set a configuration default instead of repeating the attribute:
```js
up.fragment.config.navigateOptions.transition = 'cross-fade'
```
All three **set the same option**. They differ in scope: one element, one call, or every navigation in your app.