URL Percent Encoding and Unicode

Xah Lee, 2010-05-24

This page discuss some issues about what characters should be percent encoded in URL, and how different browsers behave.

Browser Behavior

Some test on browser's behavior on URL encoding/decoding. Apparently, some browsers automatically decode parts of the percent encoding.

Copy this line:

http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_(Dürer)

then go to browser, open a new tab or window, paste the line into the URL field, then Enter ↵ to load the page.

Then, select URL field and copy the URL. Then, paste in a text editor. Here are the results (on Windows browsers):

• Google Chrome
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_(D%C3%BCrer)

• Safari
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_(Dürer)

• Firefox
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_%28D%C3%BCrer%29

• Opera
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_(Dürer)

• IE
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_(Dürer)

Now, try again, starting with this line:

http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_%28D%C3%BCrer%29

• Google Chrome
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_(D%C3%BCrer)

• Safari
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_%28Dürer%29

• Firefox
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_%28D%C3%BCrer%29

• Opera
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_(Dürer)

• IE
http://en.wikipedia.org/wiki/St._Jerome_in_His_Study_%28D%C3%BCrer%29

Another example. Start with:

http://en.wikipedia.org/wiki/Sylvester%E2%80%93Gallai_theorem

• Google Chrome
http://en.wikipedia.org/wiki/Sylvester%E2%80%93Gallai_theorem

• Safari
http://en.wikipedia.org/wiki/Sylvester–Gallai_theorem

• Firefox
http://en.wikipedia.org/wiki/Sylvester%E2%80%93Gallai_theorem

• Opera
http://en.wikipedia.org/wiki/Sylvester–Gallai_theorem

• IE
http://en.wikipedia.org/wiki/Sylvester%E2%80%93Gallai_theorem

All results are on Windows Vista, using latest public released version of the browsers as of 2010-05-24.

Summary

Here's some summary of the behavior.

• Firefox (v 3.6.3), is the most aggressive in turning characters in URL into the percent encoded form.
• Google Chrome (4.1.249.1064 (45376)) will change Unicode chars into percent encoded form, but not parenthesis chars.
• Safari (4.0.5 (531.22.7)) does convert some percent encoded chars into plain Unicode char, but not all.
• Opera (v 10.10, build 1893) is the best, it shows Unicode and paren and en-dash as is.
• IE (8.0.6001.18904), seems to take the approach that it doesn't do anything to the URL. Whatever you pasted in, remains unchanged.

Reference

• An Introduction to Multilingual Web Addresses @ www.w3.org…
• Internationalized Resource Identifier
• XRI
• Internationalized domain name
• Punycode