---
schema_version: "1"
id: ea931be6cf71faa95b278ed8f48fccb377c5a474273075bb70adf0db1fb817e5
title: <aura:if> —Clean Unrendered Body —Clean Unrendered Body
collection: developer
version: current
locale: en-us
portal_url: https://docs.salesforce.com/developer/current/en-us/platform/aura-platform/guides/aura/perf-warnings/perf-warnings-if.md
canonical_url: https://developer.salesforce.com/docs/platform/aura-platform/guide/perf-warnings-if.html
source_site: developer.salesforce.com
content_type: documentation
content_hash: 935c375e60a6028011941ad15fd6e1606a1adf9bbddac09dfb21827fa7f04bf1
products:
  - Lightning Aura Components Developer Guide
  - Platform Developer Content
---

# \<aura:if> —Clean Unrendered Body —Clean Unrendered Body

This warning occurs when you change the `isTrue` attribute of an `<aura:if>` tag from `true` to `false` in the same rendering cycle. The unrendered body of the `<aura:if>` must be destroyed, which is avoidable work for the framework that slows down rendering time.

## Example

This component shows the anti-pattern.

```nolang
<!--c:ifCleanUnrendered-->
<aura:component>
    <aura:attribute name="isVisible" type="boolean" default="true"/>
    <aura:handler name="init" value="{!this}" action="{!c.init}"/>

    <aura:if isTrue="{!v.isVisible}">
        <p>I am visible</p>
    </aura:if>
</aura:component>
```

Here’s the component’s client-side controller.

```javascript
/* c:ifCleanUnrenderedController.js */
({
    init: function(cmp) {
        /* Some logic */
        cmp.set("v.isVisible", false); // Performance warning trigger
    }
})
```

When the component is created, the `isTrue` attribute of the `<aura:if>` tag is evaluated. The value of the `isVisible` attribute is `true` by default so the framework creates the body of the `<aura:if>` tag. After the component is created but before rendering, the `init` event is triggered.

The `init()` function in the client-side controller toggles the `isVisible` value from `true` to `false`. The `isTrue` attribute of the `<aura:if>` tag is now `false` so the framework must destroy the body of the `<aura:if>` tag. This warning displays in the browser console only if you enabled debug mode.

```nolang
WARNING: [Performance degradation] markup://aura:if ["5:0"] in c:ifCleanUnrendered ["3:0"]
needed to clear unrendered body.
```

Click the expand button beside the warning to see a stack trace for the warning.

![browser console stack trace](https://developer.salesforce.com/media/aura-platform/if_stack_trace.png)

Click the link for the ifCleanUnrendered entry in the stack trace to see the offending line of code in the Sources pane of the browser console.

## How to Fix the Warning

Reverse the logic for the `isTrue` expression. Instead of setting the `isTrue` attribute to `true` by default, set it to `false`. Set the `isTrue` expression to true in the `init()` method, if needed.

Here’s the fixed component:

```nolang
<!--c:ifCleanUnrenderedFixed-->
<aura:component>
    <!-- FIX: Change default to false.
         Update isTrue expression in controller instead. -->
    <aura:attribute name="isVisible" type="boolean" default="false"/>
    <aura:handler name="init" value="{!this}" action="{!c.init}"/>

    <aura:if isTrue="{!v.isVisible}">
        <p>I am visible</p>
    </aura:if>
</aura:component>
```

Here’s the fixed controller:

```javascript
/* c:ifCleanUnrenderedFixedController.js */
({
    init: function(cmp) {
        // Some logic
        // FIX: set isVisible to true if logic criteria met
        cmp.set("v.isVisible", true);
    }
})
```

**See Also**  


-   [*Salesforce Help:* **Enable Debug Mode for Lightning Components**](https://help.salesforce.com/articleView?id=aura_debug_mode.htm)