Redoc: Failed to fetch .net core api swagger.json

[YINZHU2016]

I used.Net core API, and installed swagger plug-ins, I configured everything, and able to.

Normal access to the api/swagger address saw the swagger interface, and I started using your redoc to build my API introduction site, but when I introduced my http://{myuri}/swagger.json file, it always burst out
`Something went wrong...
Error downloading http://xxx/swagger/v1/swagger.json Failed to fetch
Stack trace
Error: Error downloading http://xxxxx/swagger/v1/swagger.json
Failed to fetch
at https://cdn.jsdelivr.net/npm/redoc@next/bundles/redoc.standalone.js:40:15553
at https://cdn.jsdelivr.net/npm/redoc@next/bundles/redoc.standalone.js:118:101808
at

TypeError: Failed to fetch

ReDoc Version: 2.0.0-alpha.17
Commit: de177a0`

I can normally open this http://xxx/swagger/v1/swagger.json address through browser and get content.
But I don't know why, because I'm a swagger document that is automatically generated through the swagger plug-in, so my document is theoretically completely consistent with the OpenAPI protocol.

can you help me

The following is the code of my.Net core related to the use of swagger

`services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new Info { Title = "xxx API", Version = "v1" });
//开启swagger对FluentValidation的支持
c.AddFluentValidationRules();
// Set the comments path for the Swagger JSON and UI.
var basePath = AppContext.BaseDirectory;
var xmlPath = Path.Combine(basePath, "xxxx.WebApi.xml");
c.IncludeXmlComments(xmlPath);

            //支持bearer token https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/603
            c.AddSecurityDefinition(Bearer, new ApiKeyScheme
            {
                In = "header",
                Description = "Please insert JWT with Bearer into field",
                Name = "Authorization",
                Type = "apiKey"
            });

            c.AddSecurityRequirement(new Dictionary<string, IEnumerable<string>>
            {
                {Bearer, new string[] { }}
            });

            c.OperationFilter<FormFileOperationFilter>();
        });`

`// Enable middleware to serve generated Swagger as a JSON endpoint.
app.UseSwagger();

        // Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.), specifying the Swagger JSON endpoint.
        app.UseSwaggerUI(c => { c.SwaggerEndpoint("../swagger/v1/swagger.json", "My API V1"); });`

[RomanHotsiy]

Something is wrong with your setup. Maybe CORS is misconfigured.
this is not an issue of redoc

[thangchung]

For those people who still cannot make it work, I found the answer at https://stackoverflow.com/questions/50623420/migrating-to-net-core-2-1-breaks-swagger-ui. Hope this help!

[mattwoberts]

I'm seeing the same issue to - I have a working swagger.json file available fpr my site, but trying to plumb it into a local redoc page gives me this error.

[divyang-desai]

Something is wrong with your setup. Maybe CORS is misconfigured.
this is not an issue of redoc

I don't think so as I'm requesting to my local project, It doesn't required CORS configuration at all. And it gives the same error. ASP.NET Core 2.2

[dfaramarzi]

Because you named your Swagger Docs "V1", you should add it in app.SwaggerEndpoint() too:

app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/V1/swagger.json", "Api"));

[ghost]

In case someone else gets the same error, I cloned an API endpoint and forgot to update the route (had a duplicate) and swagger was giving this _helpful_ error message... corrected the route and the error disappeared.

[Perustaja]

Because you named your Swagger Docs "V1", you should add it in app.SwaggerEndpoint() too:

app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/V1/swagger.json", "Api"));

Seems like I got too used to OpenAPI...I started changing strings around without understanding how everything works together. This worked for me, thanks!

[karpediemnow]

To see the effettive problem try to navigate directly to

https://localhost:port/swagger/v1/swagger.json

and analyze the output.

[brentminder]

None of the previous worked for me when i upgraded to swashbuckle 5.4 (and Microsoft.OpenApi to 1.2 preview 3).

What did work was reverting Microsoft.OpenApi back to 1.1.4.

Hope this fix works for you.

[ishmael0]

According to Microsoft:
To serve the Swagger UI at the app's root (http://localhost:/), set the RoutePrefix property to an empty string:
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
c.RoutePrefix = string.Empty;
});

[NepCode]

Be sure you're using [Http] attribute on every endpoint, example:
[HttpDelete("{id}")]

[praveen-prakash]

None of the previous worked for me when i upgraded to swashbuckle 5.4 (and Microsoft.OpenApi to 1.2 preview 3).

What did work was reverting Microsoft.OpenApi back to 1.1.4.

Hope this fix works for you.

Yes, I removed Microsoft.OpenApi Reference. and It works for me. I waist a lot times... Finally I got clue with this article.

[xuanvuong1998]

[SOLVED] The cause might be missing Http Method Annotation in Controller method

[BrunoPecanha]

To see the effettive problem try to navigate directly to

https://localhost:port/swagger/v1/swagger.json

and analyze the output.

Man, thx so much !
This way i could see what was happening

MissingMethodException: Method not found: 'Void Microsoft.OpenApi.Writers.OpenApiJsonWriter..ctor(System.IO.TextWriter)'.
Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.RespondWithSwaggerJson(HttpResponse response, OpenApiDocument swagger)
System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start(ref TStateMachine stateMachine)
System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start(ref TStateMachine stateMachine)
Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.RespondWithSwaggerJson(HttpResponse response, OpenApiDocument swagger)
Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

[benkins]

I had also just encountered this error, it was because I copied a method from another API controller, and forgot to add the Http method and route

[tmoodley]

This error was a pain to find but eventually it was staring right in my face. Copy and paste this link https://localhost:44353/swagger/v1/swagger.json into the browser and it will show you the exact error you need to fix.