ASP.NET Core Swagger Not Showing – Complete Solution Guide

Introduction

Swagger helps developers test and document APIs in ASP.NET Core. It shows all API endpoints in one place and lets you send requests from the browser.

However, many developers face a common issue:
Swagger is not showing in ASP.NET Core.

You may see:

• /swagger returning 404 Not Found
• Swagger UI not loading
• Swagger working in Development but not in Production
• The API running fine, but Swagger missing

This usually happens due to configuration or middleware issues, not because Swagger is broken.

In this guide, you will learn why Swagger does not show and how to fix it step by step using simple explanations.

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Why Swagger Is Important in ASP.NET Core

Swagger is more than just a documentation tool. It helps developers understand and test APIs quickly.

With Swagger, you can:

• See all API endpoints in one place
• Check request and response formats
• Test APIs without Postman
• Share API details with frontend teams

When Swagger does not show, development becomes slower. Teams waste time guessing API behavior. That is why fixing Swagger issues early is very important.

What Does “Swagger Not Showing” Mean?

When Swagger is not showing, it means:

• Swagger is not enabled correctly
• ASP.NET Core is blocking it
• The environment settings disable it

Swagger depends fully on your application setup.

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Common Reasons Swagger Is Not Showing

Most Swagger problems happen due to:

• Missing Swagger services
• Swagger UI middleware not enabled
• Swagger enabled only in Development
• Wrong middleware order
• Authentication blocking Swagger
• HTTPS or routing problems

Let’s fix each issue one by one.

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1. Swagger Services Not Added

Problem

Swagger UI cannot load if you do not register its services.

Solution

Add these lines in Program.cs:

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

Without this, Swagger has no API data to show.

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2. Swagger Middleware Not Enabled

Problem

Swagger services exist, but the UI does not appear.

Solution

Enable Swagger middleware:

app.UseSwagger();
app.UseSwaggerUI();

Now access Swagger at:

/swagger

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3. Swagger Works Only in Development

Problem

Swagger shows locally but not on staging or production.

Cause

Most templates enable Swagger only in Development:

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

Fix Options

Enable Swagger everywhere:

app.UseSwagger();
app.UseSwaggerUI();

Or enable for selected environments:

if (app.Environment.IsDevelopment() || app.Environment.IsStaging())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

👉 In Production, protect Swagger instead of disabling it.

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4. Wrong Middleware Order

Problem

Swagger does not load because middleware runs in the wrong order.

Correct Order

app.UseRouting();

app.UseSwagger();
app.UseSwaggerUI();

app.UseAuthentication();
app.UseAuthorization();

app.MapControllers();

Swagger should load before authentication and authorization.

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5. Swagger Blocked by Authentication

Problem

Swagger shows 401 Unauthorized or 403 Forbidden.

Cause

Global authorization rules block /swagger.

Solution

Allow Swagger access or exclude it from authorization in production.

This is a very common mistake.

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6. HTTPS Configuration Issue

Problem

Swagger fails after enabling HTTPS.

Cause

Swagger URL uses HTTP while the app runs on HTTPS.

Solution

Update Swagger endpoint:

app.UseSwaggerUI(options =>
{
    options.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
});

Always open Swagger using:

https://localhost:xxxx/swagger

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7. Wrong Launch URL or Port

Problem

The app runs, but Swagger does not open.

Solution

Check launchSettings.json:

"launchUrl": "swagger"

Also confirm:

• Correct port
• Correct launch profile

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8. Swagger Not Showing with Minimal APIs

Problem

Swagger loads but does not show Minimal API endpoints.

Solution

Make sure this line exists:

builder.Services.AddEndpointsApiExplorer();

Without it, Swagger cannot detect Minimal APIs.

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9. Swagger Not Showing on IIS or Reverse Proxy

Problem

Swagger works locally but not after deployment.

Common Fixes

• Enable forwarded headers
• Check base path
• Verify routing

app.UseForwardedHeaders();

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10. Swagger UI Loads but APIs Are Missing

Problem

Swagger UI opens, but endpoints are empty.

Fix Checklist

• Controllers use [ApiController]
• Controllers have [Route]
• Endpoints are public
• No build errors

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How to Quickly Check If Swagger Is Enabled

Before changing any code, do these quick checks:

• Open your browser and go to /swagger
• Check if the page loads or shows a 404 error
• Look at application logs for startup errors
• Confirm the app runs without exceptions

These simple checks often reveal the problem immediately.

Common Mistakes Developers Make with Swagger

Many developers repeat the same mistakes:

• Forgetting to enable Swagger in Production
• Blocking Swagger using global authorization
• Running Swagger after authentication middleware
• Forgetting AddEndpointsApiExplorer
• Using the wrong launch profile

Avoiding these mistakes saves hours of debugging time.

Best Practices for Swagger

• Secure Swagger in Production
• Do not expose private APIs
• Use API versioning
• Add XML comments
• Test Swagger after deployment

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Frequently Asked Questions (FAQ)

Why is Swagger not showing in ASP.NET Core?

Swagger usually fails due to missing middleware, environment checks, or authentication blocking access.

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What is the default Swagger URL?

/swagger

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Does Swagger work in Production?

Yes, but you must enable it manually.

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Can authentication block Swagger?

Yes. Authorization rules often block Swagger by mistake.

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Why does Swagger show a 404 error?

Swagger middleware is missing or disabled.

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Conclusion

Swagger not showing in ASP.NET Core is a common problem, especially for beginners and even experienced developers.

The good news is simple. Swagger usually fails due to configuration issues, not because of bugs in your API. Once you understand how Swagger works in the middleware pipeline, fixing the issue becomes easy.

Always start by checking:

• Swagger services
• Swagger middleware
• Environment settings
• Middleware order
• Authentication rules

By following these steps, you can make Swagger visible again and continue developing your APIs without frustration.

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Related Articles

• How to Fix 401 Unauthorized in ASP.NET Core JWT
• Authentication vs Authorization in ASP.NET Core – Complete Guide
• How to Fix CORS Error in ASP.NET Core API

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