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If you want to build a WebApp that can be used offline, or make sure your existing WebApp is offline-ready, you've come to the right place.

Your app might be unusable offline if:

  1. It needs the server to function

    OK so this one's a little obvious, but it's also pretty limiting. Your WebApp cannot make any requests to your server or other servers during offline use. That means in order for your app to be useful offline, the data: URL that is created when it is saved must contain everything it needs to work.

  2. It needs cookies

    When a data: URL is opened, the browser constructs the corresponding page without interacting with the web saver that originally provided the page. Nothing that a user did the previous time they viewed a saved page will affect the next loading of that page. User preferences, for example, would be forgotten.

  3. It needs up-to-date content

    If it is important that your users see up-to-date information each time they use your app, then a data: URL probably does not make sense for you. iWebSaver provides a link to update any page it has saved, but there is no guarantee that a user will take advantage of this when an internet connection is available.

  4. You use JavaScript to construct image names

    Finally, here's something you can control without affecting the functionality of your app (this goes for you, game designers). If your javascript does something like this:

    img=((a>b)?"a":"b")+".png"

    It is impossible to package the images being used as data: URLs because a) your script is changing url strings to control which image is fetched from the server at the time of use and b) iWebSaver can't understand the intention of your javascript. This is generally not the best way to handle presentational changes anyway. Instead try something like this (over-simplified) combination of javascript and css:

    javascript:
    class=(a>b)?"a":"b"

    css:
    .a{background:url(a.png)}
    .b{background:url(b.png)}

    Now iWebSaver can make data: URLs for the two images, since their addreses are clearly identified in your stylesheet, and your javascript can now switch between the images without making any requests to your server.

Always remember to reload and try your saved WebApp with your iPhone actually in Airplane mode before you determine that it works as you intend it to offline.

My WebApp is ready to go offline!

So your WebApp works great offline and you want to tell people about it? You can easily add a Save Offline link to any page or app. Just link to http://iWebSaver.com/?u=yoursite.com (and replace "yoursite" with the URL of your site, of course).

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