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Comment by witty_username | Hacker News Reader

> essentially no way to detect duplicate submissions

No, the shortened URL can be followed.

... and once it is followed, it is the true URL that should be displayed, because it contains more useful information for the end user, like the true domain where the article resides, instead of the alphabet soup you get with link shorteners. which, again, is why link shorteners are banned here.

i probably shouldn't engage in arguing pointless minutiae like this. i will refrain after this one.

I agree.

I think it's good to discuss HN social norms when it's appropriate. Your comment added to the discussion.

True, if anything that should be a feature of HN. To try and follow a 403 and use that instead. The only examples I can think of in which this wouldn't be desired are articles you have to login to access, but that could be a short blacklist or whitelist. Of course once we're inspecting URLs for 403s, I can see a slippery slope to indexing and comparing content of submissions...

304, not 403. And actually, only a 301 Permanent Redirect should be followed and used instead. bit.ly and URL shorteners it powers, which includes atav.st, use 301 Permanent Redirect.

Fetching the headers would also be a good way to check the MIME type (for automatic warnings like [pdf] or [video]), as well as checking the title.

Of course 304, ungh. The reason 304 gets used more often than 301 even for essentially permanent redirects is because of browser caching... If you allow editing a redirect, then you might want to change future requests. Of course, many URL shorteners don't allow edits. As far as I know, some browsers don't cache-invalidate 301s. Haven't investigated recently, maybe there's an HTTP2 solution for this, or proper use of headers, or something.

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