ESI (Edge Side Includes)

📋 Description

Edge Side Includes allows assembling web pages from fragments at the edge. This endpoint serves a parent HTML file containing ESI tags that Fastly processes to inject child content.

Internally redirects to /html/parent_esi.html.

⚙️ How ESI Works

Client Request → Fastly Edge
                 ↓
    1. Serves parent_esi.html
    2. Detects <esi:include> tags
    3. Fetches child_esi.html
    4. Assembles final HTML
                 ↓
    Complete HTML Response

📄 ESI Files

parent_esi.html
Contains ESI include tags • Cache-Control: private, no-store
child_esi.html
Content to be included • Cache-Control: private, no-store

💡 Usage Examples

Test ESI processing:

curl https://your-service.edgecompute.app/fastly_features/esi

View parent file directly:

curl https://your-service.edgecompute.app/html/parent_esi.html

View child file directly:

curl https://your-service.edgecompute.app/html/child_esi.html

🏷️ ESI Tag Syntax

In the parent HTML file:

<esi:include src="/html/child_esi.html" />

📄 Expected Response

HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
Cache-Control: private, no-store

[HTML with child content injected]

Note: ESI processing must be enabled in your Fastly service configuration. Both files use Cache-Control: private, no-store to ensure fresh processing on each request.