app.UseOutputCache() in ASP.NET Core

Output Caching is a new and powerful feature in ASP.NET Core introduced in .NET 7 that allows developers to cache full HTTP responses in memory and serve them for subsequent requests — boosting performance and reducing unnecessary processing.

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What is Output Caching?

Output caching stores the full response generated by your application (such as a Razor Page or API controller response) in server memory, so that subsequent identical requests are served from the cache instead of being regenerated.

This is especially useful for:

• Expensive computations (e.g., report generation)

• Frequently requested static or semi-dynamic content

• Improving API response times

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How to Enable Output Caching

Add OutputCache service and middleware in your Program.cs:

var builder = WebApplication.CreateBuilder(args);

// Enable Output Caching
builder.Services.AddOutputCache();

var app = builder.Build();

app.UseRouting();

// Enable the middleware
app.UseOutputCache();

app.UseEndpoints(endpoints =>
{
    endpoints.MapRazorPages();
    endpoints.MapControllers();
});

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Basic Example: Razor Page

Let’s create a simple Razor Page (/Pages/Index.cshtml) that shows a welcome message:

@page
@model IndexModel
<h1>Welcome</h1>
<p>This page is not cached by default.</p>

And its code-behind (Index.cshtml.cs):

using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.OutputCaching;

public class IndexModel : PageModel
{
    public void OnGet()
    {
        // Normal page load
    }
}

This page does not have caching by default, but you can apply policies or filters later.

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API Example with Conditional Caching

We’ll create an API that returns the current time, with optional noCache query support.

[ApiController]
[Route("api/[controller]")]
public class TimeController : ControllerBase
{
    [HttpGet("now")]
    [OutputCache(PolicyName = "TimePolicy")]
    public IActionResult GetTime([FromQuery] bool noCache = false)
    {
        if (noCache)
        {
            HttpContext.Response.Headers["Cache-Control"] = "no-store";
        }

        return Ok(new { Time = DateTime.Now });
    }
}

Then, define the policy in Program.cs:

builder.Services.AddOutputCache(options =>
{
    options.AddPolicy("TimePolicy", policy =>
    {
        policy.Expire(TimeSpan.FromSeconds(20))
              .SetVaryByQuery("noCache");
    });
});

Now, accessing /api/time/now will return a cached response for 20 seconds — unless you use ?noCache=true to bypass it.

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Output Cache vs Response Cache

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Benefits of UseOutputCache()

• Lightning-fast response times for repeated requests

• Less pressure on your application logic or database

• Fine-grained cache control using query strings, headers, routes, etc.

• Easy to implement and extend

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📦 Download Full Project

I’ve created a full ready-to-run project with:

• Razor Page example

• API with cache bypass logic

• Output cache policy configuration

👉 Download OutputCacheSample (GitHub Ready)

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💬 Final Thoughts

Output caching is a great feature for improving app performance without the complexity of external caching layers. With just a few lines of code, you can serve responses faster and keep your backend scalable.

I’m Morteza Jangjoo and “Explaining things I wish someone had explained to me”

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