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Asked: 2026-05-19T02:36:17+00:00

from Dive into HTML5: Cache Manifest: Fallback section CACHE MANIFEST FALLBACK: / /offline.html NETWORK:

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from Dive into HTML5: Cache Manifest: Fallback section

CACHE MANIFEST
FALLBACK:
/ /offline.html
NETWORK:
*

i dont understand from the URL given what this block of code exactly does. does the fallback section mean when anything is not found, show the offline.html page

then network: * all resources will be cached? it says also

It uses common CSS, JavaScript, and
images on each page. Each of these
resources would need to be listed
explicitly in the CACHE

this seems to conflict to network: * where it seems to say cache everything?

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1 Answer

  1. Editorial Team

    There are three types of headings in a cache manifest, CACHE, NETWORK and FALLBACK. Anything that is not under a heading is implicitly set under CACHE. An explanation of each section:

    CACHE: Files under this heading will be cached.

    NETWORK: Files under this heading require an internet connection and so will be NOT be cached.

    FALLBACK: Files matched by patterns under this heading (Such as the pattern “/”, which matches all files) and have not been cached, will have a fallback file shown instead.

    With regards to the block of code from Dive into HTML 5, there is an explanation of the “NETWORK: *” part just under it:

    It means that, while you’re browsing
    this hypothetical offline-enabled
    Wikipedia online, your browser will
    fetch images and videos and other
    embedded resources normally, even if
    they are on a different domain. (This
    is common in large websites, even if
    they aren’t part of an offline web
    application. HTML pages are generated
    and served locally, while images and
    videos are served from a CDN on
    another domain.) Without this wildcard
    flag, our hypothetical offline-enabled
    Wikipedia would behave strangely when
    you were online — specifically, it
    wouldn’t load any externally-hosted
    images or videos!

    The following quote:

    It uses common CSS, JavaScript, and
    images on each page. Each of these
    resources would need to be listed
    explicitly in the CACHE

    means that you must include all necessary CSS, Javascript and image files in the manifest under the CACHE heading. It does not conflict with ‘NETWORK: *’ because the NETWORK heading does NOT mean ‘cache everything’. It actually means the opposite: that everything under the NETWORK heading requires an internet connection and should not be cached.

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