---
description: Introduction to the built-in renderers.
---

# Build custom renderers

## 3. Observe the built-in renderers

First, visit [the advanced playground](https://blockly-demo.appspot.com/static/tests/playgrounds/advanced_playground.html) to observe what the built-in renderers look like.

Click on the "Loops" entry and drag out a repeat block. Now, change the selection in the "renderer" drop down to observe the look of each built-in renderer. By default, the renderer named "Geras" is used.
