Fetching a Blob with no MIME type set spec/interop issue

[Domenic Denicola]

Hi folks,

We got a request from Anne to engage on this GitHub issue. All three browsers do different things when looking at the Content-Type header of the Response object returned when fetch()ing a Blob() created with no MIME type.

I'm not sure we have any strong opinions, but if we're willing to align with the current favorite of Safari's approach (an empty string), having someone from Chromium say that publicly would help move the spec process along. (Of course, if we have strong opinions, those are also welcome.)

Best,

Domenic

[Ayu Ishii]

Hey Domenic,

Thanks for bringing this up.
No strong opinions from the storage team, aligning with Safari sounds good to us.
Responded to the github issue.

Best,
Ayu

[Domenic Denicola]

Thanks so much!

[guest271314]

If I read the GitHub issue correctly, Firefox 105 returns "text/plain; charset=utf-8", Chromium 108 Dev Channel returns "text/html; charset=utf-8" when running this at console

var blob = new Blob([]);
var url = URL.createObjectURL(blob);
fetch(blob).then((r) => r.headers.get('content-type'))
.then(console.log, console.error);

The "text/plain" I can understand, an empty string. I don't understand "text/html".

I don't know how"application/x-unknown-content-type" got returned anywhere in the test in the GitHub issue. Are you sure that is what is returned by Firefox; it looks like that was just a parameter passed to the function?

I don't think the browser should return an empty string when it doesn't recognize the MIME type. I haven't seen that brought up; mentioning here so whatever decision is made re no MIME type overflows to unrecognized MIME type get converted to empty string.

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[guest271314]

Ah, I was fetching the Blob, not the ObjectURL. null for Chromium 108, application/x-unknown-content-type for Firefox 105.

On Mon, Oct 3, 2022 at 4:26 PM Ayu Ishii <ay...@chromium.org> wrote:

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