Rory O'Kane Rory O'Kane - 1 year ago 59
HTML Question

How do I link to a file to download that a browser can’t view?

In HTML, how do you link to a file that the browser can only download, not view? For instance, say I have a zip file, I want visitors to my website to be able to download that file when they click a link. The link would look like this: download my program. On my webserver, the HTML file and the zip file are in the same directory, so the relative path of the zip file is simply its filename.

But if I just link to the file with an

<a href="">
tag, the browser wouldn’t recognize the link, right? Because browsers can’t open zip files. So what is the proper way to link to it?

Answer Source

Actually, your example is the proper way to link to the file:

<a href="">download my program</a>

You can never tell for sure that a browser can’t view a file. You just link to it; it’s up to the browser to do what they think best with it – display it, download it, or do something else. Don’t worry; browsers will generally do the right thing.

This follows the principle of the web that you don’t know what the browser will do with the files and pages you send it. You mentioned a ZIP file, but think of PDF files. They are like a ZIP file: they are not HTML, they are not made for a browser, and the browser might download it. But there are plugins such as Adobe PDF Reader and Schubert’s PDF Browser Plugin that show the contents of the PDF file right in the browser. Similarly, hypothetically, there might be a ZIP file viewer for the browser – it might show the user the contents of the ZIP file in the browser and let the user decide where to extract those contents.

Most browsers don’t have the hypothetical ZIP file viewer described, so the file will just download, like you wanted. But that doesn’t really matter; just write your link and everything will be okay.

The browser could do things other than viewing the file or downloading the file right away. It could also ask the user if they want to download the file. Or it could start downloading the file, detect a virus in it, and delete it right away. The point is, it’s up to the browser what it does with the file.

Note that this policy goes the other way. Your HTML pages look to the browser just like files look – they are both “resources”. “Resource” is the “R” in “URL”. When you visit an HTML page by visiting a URL, the browser thinks “this is an HTML resource. What should I do with this? Oh, I can display it in the main window – I’ll do that.” This is the same process as downloading a ZIP file after clicking a link to its URL, where it thinks “this is a ZIP resource. What should I do with this? I can’t display it – I guess I’ll start downloading it and open the downloads window so the user can see what happened.” Most browsers even let you download the HTML of a page just like a file, if you ask it to.

If you have multiple formats of your file, and want to let the browser choose the best one it can view, then you could set up a system using the HTTP Accept header. For instance, if you had both a ZIP and a RAR version of my-program, then you could make it so you link to just my-program and the browser chooses the version it likes best. But the setup for that can be complicated, and that kind of system isn’t usually necessary for just a file download. The Accept header is usually used to get the correct version of something that the browser is meant to view – for instance, the browser might choose an MP4 video file over a WMV video file because it doesn’t have any codec that can play embedded WMV videos.

If you want to force the browser to download a file even though the browser can probably view it on its own, see this question.

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