Response Caching

Response caching reduces the number of requests a client or proxy makes to a web server. See the Microsoft documentation for details of Response caching in ASP.NET Core and how to implement the Response Caching Middleware.

Modify the Cache-Control header for Static Files

Example class to allow the modification of the Cache-Control header for static assets by file extension, but excluding Umbraco BackOffice assets.

using System.IO;
using System;
using System.Collections.Generic;

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Options;
using Microsoft.AspNetCore.Http.Headers;
using Microsoft.Net.Http.Headers;

using Umbraco.Cms.Core.Configuration.Models;
using IHostingEnvironment = Umbraco.Cms.Core.Hosting.IHostingEnvironment;

namespace Umbraco.Docs.Samples.Web.Tutorials
{
    public class ConfigureStaticFileOptions : IConfigureOptions<StaticFileOptions>
    {
        // These are the extensions of the file types we want to cache (add and remove as you see fit)
        private static readonly HashSet<string> _cachedFileExtensions = new(StringComparer.OrdinalIgnoreCase)
        {
            ".ico",
            ".css",
            ".js",
            ".svg",
            ".woff2",
            ".jpg"
        };

        private readonly string _backOfficePath;

        public ConfigureStaticFileOptions(IOptions<GlobalSettings> globalSettings, IHostingEnvironment hostingEnvironment)
            => _backOfficePath = globalSettings.Value.GetBackOfficePath(hostingEnvironment);

        public void Configure(StaticFileOptions options)
            => options.OnPrepareResponse = ctx =>
            {
                // Exclude Umbraco backoffice assets
                if (ctx.Context.Request.Path.StartsWithSegments(_backOfficePath))
                {
                    return;
                }

                // Set headers for specific file extensions
                var fileExtension = Path.GetExtension(ctx.File.Name);
                if (_cachedFileExtensions.Contains(fileExtension))
                {
                    ResponseHeaders headers = ctx.Context.Response.GetTypedHeaders();

                    // Update or set Cache-Control header
                    CacheControlHeaderValue cacheControl = headers.CacheControl ?? new CacheControlHeaderValue();
                    cacheControl.Public = true;
                    cacheControl.MaxAge = TimeSpan.FromDays(365);
                    headers.CacheControl = cacheControl;
                }
            };
    }
}

Register the service in Startup.cs

public void ConfigureServices(IServiceCollection services)
{
	services.AddTransient<IConfigureOptions<StaticFileOptions>, ConfigureStaticFileOptions>();

Modify the Cache-Control header for ImageSharp.Web

For setting Cache-Control max-age header for images processed by the ImageSharp middleware, you can set the Umbraco:CMS:Imaging:Cache:BrowserMaxAge setting.

See the Images Settings article for more information.

Add the Cache-Control header for rendering using the ResponseCache attribute

For example using a custom Default Controller you can add the ResponseCache attribute to the Index method

public class DefaultController : RenderController
{
    public DefaultController(ILogger<RenderController> logger, ICompositeViewEngine compositeViewEngine, IUmbracoContextAccessor umbracoContextAccessor) : base(logger, compositeViewEngine, umbracoContextAccessor)
    {
    }

    [ResponseCache(NoStore = true, Location = ResponseCacheLocation.None)]
    public override IActionResult Index()
    {
        return CurrentTemplate(new ContentModel(CurrentPage));
    }
}