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The IEInternals blog covers each browser's behavior for underrunning the purported Content-Length of a download: http://blogs.msdn.com/b/ieinternals/archive/201

by tiles 15y ago

The IEInternals blog covers each browser's behavior for underrunning the purported Content-Length of a download: http://blogs.msdn.com/b/ieinternals/archive/2011/03/09/browsers-accommodate-incorrect-http-content-length-and-sites-depressingly-depend-on-it.aspx http://blogs.msdn.com/b/ieinternals/archive/2011/03/09/brows... Looks like using browser sniffing, you can deliver an exaggerated Content-Length to everyone but Opera and browsers will deal with it gracefully. Pretty neat. (Obviously not desirable for violating the HTTP spec, but the UX gains might be worth it.)

pornel 15y ago
You're not always dealing with the client that is specified in the UA string. Clients can use proxies, including transparent proxies. For example major mobile operators pipe HTTP connections through a proxy that recompresses images. In that case you see e.g. Safari's or Opera's UA string, but you're actually dealing with proxy's HTTP behavior.
- tiles 15y ago
  In dump.ly's use case, they would probably want client-side detection in JavaScript, not the UA string. You definitely have to be conservative implementing such an unexpected feature. An older article (2008) that also talks about misreporting content-length for fun and profit: http://tech.hickorywind.org/articles/2008/05/23/content-length-mostly-does-not-matter-the-reverse-bob-barker-rule http://tech.hickorywind.org/articles/2008/05/23/content-leng...
  - gilini 15y ago
    Client-side detection in JavaScript or UA string aren't mutually exclusive, since the UA string is exposed on the DOM. Are suggesting they would rather guess the browser by inference through presence of DOM properties and methods? In the end it narrows down to: would you rather a) break the functionality for some users in exchange to give the best possible solution to others, or b) give an OK experience to everyone I usually go with "b". I think that frustration is much more powerful than awe.

by tiles 15y ago

pornel 15y ago

You're not always dealing with the client that is specified in the UA string. Clients can use proxies, including transparent proxies. For example major mobile operators pipe HTTP connections through a proxy that recompresses images. In that case you see e.g. Safari's or Opera's UA string, but you're actually dealing with proxy's HTTP behavior.

tiles 15y ago
In dump.ly's use case, they would probably want client-side detection in JavaScript, not the UA string. You definitely have to be conservative implementing such an unexpected feature. An older article (2008) that also talks about misreporting content-length for fun and profit: http://tech.hickorywind.org/articles/2008/05/23/content-length-mostly-does-not-matter-the-reverse-bob-barker-rule http://tech.hickorywind.org/articles/2008/05/23/content-leng...
- gilini 15y ago
  Client-side detection in JavaScript or UA string aren't mutually exclusive, since the UA string is exposed on the DOM. Are suggesting they would rather guess the browser by inference through presence of DOM properties and methods? In the end it narrows down to: would you rather a) break the functionality for some users in exchange to give the best possible solution to others, or b) give an OK experience to everyone I usually go with "b". I think that frustration is much more powerful than awe.