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I am aware that iPad does not have a file-system in traditional sense.

I want to know how Safari for iOS behaves when trying to download/upload files from/to a website.

Suppose I go to sourceforge.net and click on a link to download zip file? Would Safari download it? If yes, where does it get stored and how do I access it (without using iTunes to first move it to a PC).

Does Safari on iOS allow the downloading of only some files and reject others, or does it allow downloading all of them or rejects all of them?

Lastly, if a webpage has a file upload control (input type="file"), how does Safari behave (would it allow upload, allow upload on only some sites or the download control does not work at all)?

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Please note - this question is about iOS 5 and before behavior. Now iOS 6 is starting to expand the ability to upload pictures in text fields, so in time, this answer may only serve as documentation of how things were and not as they are at or past iOS 6.0. –  bmike Oct 6 '12 at 14:31
    
Okay thanks for the follow-up Mike... –  r_honey Oct 6 '12 at 18:13

2 Answers 2

up vote 4 down vote accepted

Actually the iOS does have a filesystem, and each app gets access to a sandboxed portion of the file system.

The iOS "system" itself has several programs that do access the filesystem directly, but mobile safari acts more like a restricted app purchased from iTunes than say springboard or the app store app itself.

Uploads are basically impossible in iOS. Mobile Safari doesn't read from the address book (which most sandboxed apps can and will do by default). It also doesn't use the photo picker to upload pictures or video.

Downloads are possible, but often require a helper app to store and use the download. Safari handles mp3, streams, and other media itself and lets you listen or watch the "download". You can't save it in the way a computer allows, but the web server thinks a download happened and safari actually downloads the file to it's cache (where it stays until the cache fills and it ages out and gets deleted). All other file types are handled as the iOS uses UTI file detectors to see which apps installed can handle a potential download. (The developer document I linked to has several paragraphs readable by anyone, but it dives into developer minutia very quickly so feel free to bail on that link before the simple idea behind UTI gets confused)

If safari detects another app has registered for a download, you will see an "open in apptastic" to indicate that mobile safari will download that file but hand it off to another app to store in that app's sandbox.

Safari uses a system API call to have the iOS do the writing across sandboxes.


Since you asked about a zip file, all you need on your iPad is to find an app that tells iOS it can handle zip files, and as long as the sourceforge servers send enough data for mobile safari to detect a zip file, you can download it over to your app. The reverse trip is harder, your ZIP app can't really push a file to safari for upload. Your app has to be programmed to log into sourceforge directly and call the upload API itself. (which technically will probably use the mobile safari code / webkit to do a http upload - but that all happens behind the scenes, not in what we see and control as mobile safari with the blue compass icon)

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Mobile Safari itself cannot store files for you (without jailbreaking). However some Apps like Dropbox register with Safari and enable limited support for some filetypes.

File inputs are just disabled/greyed out on Mobile Safari.

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+1 was just about to give the exact same answer but you hit submit before me. Evernote is another app that registers for downloads like that. –  jmlumpkin Sep 22 '11 at 12:14
    
Please include a reference or remove the line about jailbreaking please. To my knowledge, Mobile Safari's behavior cannot be altered to allow for the direct downloading or uploading of a file. –  cksum Sep 22 '11 at 16:18
    
At least in the past there have been plugins for Mobile Safari on jailbroken iPhones to enable downloads. I don't speak from experience but I do think it is worth mentioning, and Google returns quite a few, though possibly out-dated results. –  Gerry Sep 22 '11 at 17:13
    
+1. Dropbox is a big help for files Safari otherwise doesn't support. And by saving files to your Public Dropbox directory, you can get links to them, which can be useful in some cases, even if it's not direct upload. –  robmathers Sep 22 '11 at 17:22

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