---
title: 15. Formatter
---
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The IntelliJ Platform includes a powerful framework for implementing formatting for custom languages.
A formatter enables reformatting code automatically based on code style settings.
The formatter controls spaces, indents, wrap, and alignment.

**Reference**: [Code Formatter](/reference_guide/custom_language_support/code_formatting.md) 

* bullet list
{:toc}

## 15.1. Define a Block
The formatting model represents the formatting structure of a file as a tree of [`Block`](upsource:///platform/lang-api/src/com/intellij/formatting/Block.java) objects, with associated indent, wrap, alignment and spacing settings.
The goal is to cover each PSI element with such a block. 
Since each block builds its children's blocks, it can generate extra blocks or skip any PSI elements.
Define `SimpleBlock` based on [`AbstractBlock`](upsource:///platform/lang-impl/src/com/intellij/psi/formatter/common/AbstractBlock.java)

```java
{% include /code_samples/simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleBlock.java %}
```

## 15.2. Define a Formatting Model Builder
Define a formatter that removes extra spaces except for the single spaces around the property separator.
For example, reformat "foo  = &nbsp;&nbsp;&nbsp;&nbsp;bar" to `foo = bar`.
Create `SimpleFormattingModelBuilder` by subclassing [`FormattingModelBuilder`](upsource:///platform/lang-api/src/com/intellij/formatting/FormattingModelBuilder.java).

```java
{% include /code_samples/simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleFormattingModelBuilder.java %}
```

## 15.3. Register the Formatter
The `SimpleFormattingModelBuilder` implementation is registered with the IntelliJ Platform in the plugin configuration file using the `com.intellij.lang.formatter` extension point. 

```xml
 <extensions defaultExtensionNs="com.intellij">
    <lang.formatter language="Simple"  
            implementationClass="org.intellij.sdk.language.SimpleFormattingModelBuilder"/>
  </extensions>
```

## 15.4. Run the Project
Add some extra spaces around the `=` separator between `language` and `English`.
Reformat the code by selecting **Code \| Show Reformat File Dialog** and choose **Run**.

![Formatter](img/formatter.png){:width="800px"}