---
schema_version: "1"
id: 01bf01b2211b41820797718a9be171593f039276fd631f1e77bd535f11801faf
title: Improve Page Load Performance on Custom Pages
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/release-notes/264-0-0/rn_improve_page_load_performance.md
canonical_url: https://help.salesforce.com/s/articleView?id=release-notes.rn_improve_page_load_performance.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 838ab1ff2930999f64cbbbeb68de3ed2db9a3cf866f231b3368e4b30038d3b80
description: Speed up page loads in Chrome on custom pages that reference external scripts by adding the defer attribute to your script tags. Custom pages include those in managed packages, such as Apex pages, Visualforce pages, and Lightning container components.
products:
  - Cross Cloud
release: "264"
---
# Improve Page Load Performance on Custom Pages

Speed up page loads in Chrome on custom pages that reference external scripts by adding the `defer` attribute to your `script` tags. Custom pages include those in managed packages, such as Apex pages, Visualforce pages, and Lightning container components.

**Where:** This change applies to Lightning Experience and Salesforce Classic in Enterprise, Performance, Unlimited, and Developer editions.

**Why:** Salesforce renders Content Security Policy (CSP) as a `meta` tag. In Chrome, this causes external scripts to download one at a time, which slows page loads. The `defer` attribute restores parallel download and preserves execution order.

**How:** To restore parallel downloads on custom pages, add `defer`\="true" to each script tag. For example:

```
<script src="https://example.com/library.js" defer="true"></script>
```

![Note](https://sf-zdocs-cdn-prod.zoominsoftware.com/tdta-release-notes-salesforce_release_notes-264-0-0-production-enus/550ba85b-db1a-4608-9cd4-9a65ec96e1fa/images/icon_note.png)

Note The `async` attribute also triggers parallel downloads, but it doesn't presever execution order. Use `defer` for most pages. Scripts with `defer` run after the page is parsed, so inline scripts depend on them must wait until they load.