Why my ajax showing preflight is invalid redirect error

Question

I tried the following code in Postman and it was working  Is there something wrong with the code     ajax      url   http   api example com users get      type   POST      headers           name-api-key   ewf45r4435trge            data           uid  36           success  function data          console log data              I got this error in my console as below  please advise      XMLHttpRequest cannot load http   api example com users get Response   for preflight is invalid  redirect

User · Answer

I received the same error when I tried to call https web service as http webservice.

e.g when I call url 'http://api.example.com/users/get'
which should be 'https://api.example.com/users/get'

This error is produced because of redirection status 302 when you try to call http instead of https.

User · Answer

This answer goes over the exact same thing  although for angular  -- it is a CORS issue   One quick fix is to modify each POST request by specifying one of the  Content-Type  header values which will not trigger a  preflight    These types are    application x-www-form-urlencoded multipart form-data text plain   ANYTHING ELSE triggers a preflight   For example     ajax      url   http   api example com users get      type   POST      headers           name-api-key   ewf45r4435trge          Content-Type   application x-www-form-urlencoded           data           uid  36           success  function data          console log data

User · Answer

The error indicates that the preflight is getting a redirect response  This can happen for a number of reasons  Find out where you are getting redirected to for clues to why it is happening  Check the network tab in Developer Tools   One reason  as  Peter T mentioned  is that the API likely requires HTTPS connections rather than HTTP and all requests over HTTP get redirected  The Location header returned by the 302 response would say the same url with http changed to https in this case   Another reason might be that your authentication token is not getting sent  or is not correct  Most servers are set up to redirect all requests that don t include an authentication token to the login page  Again  check your Location header to see if this is where you re getting sent and also take a look to make sure the browser sent your auth token with the request   Oftentimes  a server will be configured to always redirect requests that don t have auth tokens to the login page - including your preflight OPTIONS requests  This is a problem  Change the server configuration to permit OPTIONS requests from non-authenticated users

User · Answer

Please set http content type in header and also make sure the server is authenticating CORS  This is how to do it in PHP     NOT A TESTED CODE header  Content-Type  application json charset UTF-8    header  Access-Control-Allow-Origin       header  Access-Control-Allow-Methods  DELETE  HEAD  GET  OPTIONS  POST  PUT    header  Access-Control-Allow-Headers  Content-Type  Content-Range  Content-Disposition  Content-Description    header  Access-Control-Max-Age  1728000      Please refer to   http   www w3 org TR cors  cross-origin-request-with-preflight-0   How does Access-Control-Allow-Origin header work

User · Answer

I had the same problem and it kept me up for days  At the end  I realised that my URL pointing to the app was wrong altogether  example   URL   http   api example com   URL   https   api example com      If it s http or https verify  Check the redirecting URL and make sure it s the same thing you re passing along

User · Answer

My problem was that POST requests need trailing slashes

User · Answer

My problem was caused by the exact opposite of  ehacinom  My Laravel generated API didn t like the trailing     on POST requests  Worked fine on localhost but didn t work when uploaded to server

User · Answer

I had the same error  though the problem was that I had a typo in the url  url   http   api example com TYPO    The API had a redirect to another domain for all URL s that is wrong  404 errors    So fixing the typo to the correct URL fixed it for me

[javascript] Why my $.ajax showing "preflight is invalid redirect error"?

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