README.md

prerender-aspnetcore

ASP.NET Core middleware for Prerender.io. Intercepts requests from bots and crawlers and serves prerendered HTML, so your JavaScript-rendered app is fully indexable by search engines and social media scrapers.

Compatible with ASP.NET Core 8+ and .NET 8+.

Installation

dotnet add package Prerender.AspNetCore

Setup

Register the middleware in Program.cs:

builder.Services.AddPrerender();

var app = builder.Build();
app.UsePrerender(); // place before routing middleware

Add your token to appsettings.json:

{
  "Prerender": {
    "Token": "YOUR_PRERENDER_TOKEN"
  }
}

The middleware must be placed before routing to intercept bot requests early.

Settings

Setting	Default	Description
Prerender:Token	null	Your Prerender.io token
Prerender:ServiceUrl	https://service.prerender.io/	Prerender service URL (override for self-hosted Prerender)

Self-hosted Prerender

{
  "Prerender": {
    "ServiceUrl": "http://your-prerender-server:3000"
  }
}

How it works

Requests are prerendered when all of the following are true:

• The HTTP method is GET
• The User-Agent matches a known bot/crawler (Googlebot, Bingbot, Twitterbot, GPTBot, ClaudeBot, etc.)
  — OR the URL contains _escaped_fragment_
  — OR the X-Bufferbot header is present
• The URL does not end with a static asset extension (.js, .css, .png, etc.)

Everything else passes through to your normal ASP.NET Core pipeline.

If the Prerender service is unreachable, the middleware falls back gracefully and serves the normal response.

License

MIT