Getting “TypeError: failed to fetch” when the request hasn't actually failed

Question

I'm using fetch API within my React app. The application was deployed on a server and was working perfectly. I tested it multiple times. But, suddenly the application stopped working and I've no clue why. The issue is when I send a get request, I'm receiving a valid response from the server but also the fetch API is catching an exception and showing TypeError: failed to fetch. I didn't even made any changes to the code and it's the issue with all of the React components.

I'm getting a valid response.

But also getting this error at the same time.

fetch(url)
.then(res => res.json())
.then(data => {
  // do something with data
})
.catch(rejected => {
    console.log(rejected);
});

When I remove credentials: "include", it works on localhost, but not on the server.

I tried every solution given on StackOverflow and GitHub, but it's just not working out for me.

Answer 1

The issue could be with the response you are receiving from back-end. If it was working fine on the server then the problem could be with the response headers. Check the Access-Control-Allow-Origin (ACAO) in the response headers. Usually react's fetch API will throw fail to fetch even after receiving response when the response headers' ACAO and the origin of request won't match.

Answer 2

Note that there is an unrelated issue in your code but that could bite you later: you should return res.json() or you will not catch any error occurring in JSON parsing or your own function processing data.

Back to your error: You cannot have a TypeError: failed to fetch with a successful request. You probably have another request (check your "network" panel to see all of them) that breaks and causes this error to be logged. Also, maybe check "Preserve log" to be sure the panel is not cleared by any indelicate redirection. Sometimes I happen to have a persistent "console" panel, and a cleared "network" panel that leads me to have error in console which is actually unrelated to the visible requests. You should check that.

Or you (but that would be vicious) actually have a hardcoded console.log('TypeError: failed to fetch') in your final .catch ;) and the error is in reality in your .then() but it's hard to believe.

Answer 3

I have a similar problem and as I'm newbie, here are some facts for somebody to comment:

I'm sending form data to Google sheet this way (scriptURL is https://script.google.com/macros/s/AKfy..., showSuccess() is showing a simple image):

fetch(scriptURL, {method: 'POST', body: new FormData(form)})
.then(response => showSuccess())
.catch(error => alert('Error! ' + error.message))

Executed in Edge my HTML doesn't show error and Network tab reports this 3 requests:

Executed in Chrome my HTML (index.htm) shows Failed to fetch error and Network tab reports this 2 requests:

The value in the second column is blocked:other and there is also an error in Console tab:

GET https://script.googleusercontent.com/macros/echo?user_content_key=D-ABF... net::ERR_BLOCKED_BY_CLIENT

In order to suspend installed Chrome extensions, I executed my code in an Incognito window and there is no error message and Network tab reports this 2 requests:

My guess is that something (extension?) prevents Chrome to read the request's answer (the GET request is blocked).