unicode - Should I use accented characters in URLs?

Question

When one creates web content in languages different than English the problem of search engine optimized and user friendly URLs emerge.

I'm wondering whether it is the best practice to use de-accented letters in URLs -- risking that some words have completely different meanings with and without certain accents -- or it is better to stick to the usage of non-english characters where appropriate sacrificing the readability of those URLs in less advanced environments (e.g. MSIE, view source).

"Exotic" letters could appear anywhere: in titles of documents, in tags, in user names, etc, so they're not always under the complete supervision of the maintainer of the website.

A possible approach of course would be setting up alternate -- unaccented -- URLs as well which would point to the original destination, but I would like to learn your opinions about using accented URLs as primary document identifiers.

Answer 1

There's no ambiguity here: RFC3986 says no, that is, URIs cannot contain unicode characters, only ASCII.

An entirely different matter is how browsers represent encoded characters when displaying a URI, for example some browsers will display a space in a URL instead of '%20'. This is how IDN works too: punycoded strings are encoded and decoded by browsers on the fly, so if you visit café.com, you're really visiting xn--caf-dma.com. What appears to be unicode chars in URLs is really only 'visual sugar' on the part of the browser: if you use a browser that doesn't support IDN or unicode, the encoded version won't work because the underlying definition of URLs simply doesn't support it, so for it to work consistently, you need to % encode.