I think it’s safer to exclude the /umbraco folder.

Why do you think so? Static files used by the backoffice aren't supposed to change too, isn't it?

Doesn’t Umbraco already set its own cache-control header for /umbraco and package files etc.? Or are all the backoffice file caches properly invalidated using querystring or based on another cache busting technique? I would think you don’t want to enforce a very strict cache protocol for the backoffice files to prevent issues after updating Umbraco or one of the packages.

I also change the max-age for frontend files to improve page load and PageSpeed Insights scores. But for the backoffice I’d rather use no cache than adding a cache protocol that could potentially cause issues after upgrading Umbraco of packages.

Also, did you test to see if your solution does not interfere with ImageSharp? If it doesn't I'm curious to hear when you're calling UseStaticFiles() in Startup.cs.

Did you try this solution: https://our.umbraco.com/forum/umbraco-9/107501-add-cache-control-header-for-static-files-starjs-starcss-starwoff2-etc#comment-334432 ?

For me this works just fine on v9.5.0 and v10.0.1.

Yeah I finally tried that last night and it seems to work OK. I came to the conclusion we just have to throw out UseStaticFiles() completely in order to utilize crops and ImageSharp manipulation while maintaining content-cache.

Hey Pascal, I just tested your solution on Umbraco 10 and it works great! Thank you!

The only problem I have right now is with Smidge js/css files. For some reason Smidge is overwriting whatever cache header I set with: cache-control: public, max-age=864000, s-maxage=864000

Anyone has figured out a way to change max-age on Smidge generated files?

Hi João

 services.Configure<SmidgeOptions>(options =>
            {
                options.DefaultBundleOptions.ProductionOptions.CacheControlOptions.CacheControlMaxAge = 365*24;
            });

This worked for me

Hi David

Have you tried this which has been documented now: https://docs.umbraco.com/umbraco-cms/reference/response-caching#modify-the-cache-control-header-for-static-files

and furthermore the Cache-Control header for images processed by ImageSharp:
https://docs.umbraco.com/umbraco-cms/reference/response-caching#modify-the-cache-control-header-for-imagesharp.web

I'm currently using the following solution on an Umbraco 13 site and everything seems to be working just fine. The Cache-Control header is being added to CSS, JS, fonts, images and /media files.

// Add Cache-Control header to static files
builder.Services.Configure<StaticFileOptions>(options =>
{
    options.OnPrepareResponse = ctx =>
    {
        // Skip files from Umbraco backoffice / packages
        if (ctx.Context.Request.Path.StartsWithSegments("/umbraco") || ctx.Context.Request.Path.StartsWithSegments("/App_Plugins"))
            return;

        // Set specific cache-control response header
        var responseHeaders = ctx.Context.Response.GetTypedHeaders();
        var cacheControl = responseHeaders.CacheControl ?? new CacheControlHeaderValue();

        cacheControl.Public = true;
        cacheControl.MaxAge = TimeSpan.FromSeconds(31536000);
        responseHeaders.CacheControl = cacheControl;
    };
});

This needs to be called before builder.Build().

Arjan,

Is this in the ConfigureServices method or the Configure method. Can you share a little more of the setup.cs file.

I want to double check exactly where you have this

I'm only using a Program.cs, see this blog post.

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);

var config = builder.Configuration;

builder.CreateUmbracoBuilder()
    .AddBackOffice()
    .AddWebsite()
    .AddDeliveryApi()
    .AddComposers()
    //.SetContentLastChanceFinder<PageNotFoundContentFinder>()
    .Build();

// Register custom services
builder.RegisterApplicationServices(config);

WebApplication app = builder.Build();

await app.BootUmbracoAsync();

// Configure custom middleware after Umbraco boot
app.ConfigureMiddleware(config);

app.UseUmbraco()
    .WithMiddleware(u =>
    {
        u.UseBackOffice();
        u.UseWebsite();
    })
    .WithEndpoints(u =>
    {
        u.UseInstallerEndpoints();
        u.UseBackOfficeEndpoints();
        u.UseWebsiteEndpoints();
    });

// Show config debug information
app.SetDebugInfoEndpoint(config);

await app.RunAsync();

The Cache-Control code is inside my custom RegisterApplicationServices() extension method:

namespace Application.Core.Startup
{
    public static class ServicesInitializer
    {
        public static WebApplicationBuilder RegisterApplicationServices(
            this WebApplicationBuilder builder,
            ConfigurationManager config)
        {
            [...]

            // Add Cache-Control header to static files
            builder.Services.Configure<StaticFileOptions>(options =>
            {
                options.OnPrepareResponse = ctx =>
                {
                    // Skip files from Umbraco backoffice / packages
                    if (ctx.Context.Request.Path.StartsWithSegments("/umbraco") || ctx.Context.Request.Path.StartsWithSegments("/App_Plugins"))
                        return;

                    // Set specific cache-control response header
                    var responseHeaders = ctx.Context.Response.GetTypedHeaders();
                    var cacheControl = responseHeaders.CacheControl ?? new CacheControlHeaderValue();

                    cacheControl.Public = true;
                    cacheControl.MaxAge = TimeSpan.FromSeconds(31536000);
                    responseHeaders.CacheControl = cacheControl;
                };
            });

            [...]
        }
    }
}