html cache-control=no-cache changes to cache-control=max-age=0

user_3558269 0
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I've built a simple page to test the cache-control and I'm getting confused by the results. The page is just

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>Website teste</title>
    <meta http-equiv="cache-control" content="no-cache">
</head>
<body>
    <div>Hello World</div>

    <script>
        setTimeout(function () {
            window.location.reload()
        }, 10000)
    </script>
</body>
</html>

If I do a hard-refresh the cache-control is what expected enter image description here

but the next refresh the cache-control changes to max-age=0

enter image description here

And shouldn't the result be a 304 (Not Modified) instead a 200 (OK)

This sample site is running on VisualStudio (IIS)

cache-control http-headers html
1 Answers

The http-equiv attribute of the meta element is defined in the HTML standard. Note that:

The http-equiv attribute is an enumerated attribute. The following table lists the keywords defined for this attribute...

cache-control is not one of the listed values, and thus this directive has no effect.

Your assumption isn't unreasonable, though; in earlier versions of the standard it was suggested that servers could create headers based on this element:

HTTP servers may read the content of the document <HEAD> to generate header fields corresponding to any elements defining a value for the attribute HTTP-EQUIV. NOTE - The method by which the server extracts document meta-information is unspecified and not mandatory.

I have no idea whether any servers actually did this, though.

Finally, note that the Cache-Control header you're looking at in the developer tools is a request header, not a response header, and thus has nothing to do with any of this. It's something that browsers often add to the request on refresh to make sure they don't get served cached content.

user_23957960
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