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Editorial Team
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Asked: 2026-05-13T14:12:53+00:00

What does the following HTTP 1.1 header mean? If-None-Match: * I understand it when

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What does the following HTTP 1.1 header mean?

If-None-Match: *

I understand it when using a strong or weak ETag or even a list of ETags, but I don’t understant it’s use when using star (*).

Edit: Would be nice to have some pseudocode (PHP code good also) that would show how/what to answer to “If-None-Match: *”.

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1 Answer

  1. Editorial Team

    The answer is: it depends.

    Suppose we have received

    If-None-Match: *
If-Modified-Since: <yesterday date>

    And the page has been altered today.

    First, we take a look at the * which tells us: “Return 304 if the resource is there and condition (2) is met”. Fine, the resource exists, BUT condition (2) states: “Only return 304, if the date is later than current”. So this condition is not met, and the page will be delivered completely.

    If we hadn’t received If-Modified-Since, the response would have been 304.

    If the resource hadn’t existed upon request, we’d have returned the appropriate code (as if there was no If-None-Match).

    304 should only be returned in response for GET and HEAD requests, and all cache-related response headers have to be there. For all other types of request your server needs to be answering 412 (Precondition failed).

    I hope it helps 😉

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