The current redirect is a 303 See Other (See https://github.com/joomla/joomla-cms/blob/staging/libraries/cms/application/cms.php#L971)

A 301 redirect is 301 Moved Permanently.

Right but for search engines better to use 301 redirect, that's what fixed

Yes, i know. But a 301 redirect is "Permanent".
The language plugin redirects on each page load to the default/selected language that can use different URLs, so IMHO the redirect shouldn't be permanent.

With 303 status we have duplicates in serach index, it is more seriouse problem. I see many pepople looking for solution how to fix it and do a lot of hard code fixed inside of core. This is the right place where it should be fixed. For more flexible solution we can add parameter "Redirect status".

Sample:
with 303 redirect google will store both URLs in index
domain-name.com/contact -> domain-name.com/en/contact
with 301 redirect only the last one

For other languges we have tag and site map.

I have tested this item successfully on ae373fc

I have tested this issue succesfully:
Build a multilingual site with 2 languages, set to display including their language codes (NL and EN). When going to the default page (example.com), I am redirected to the default language (example.com/en).
Before the patch was applied this was done with a 303-redirect.
After applying the test, I got a 301-redirect.

And to add to my test: I agree that 301-redirects are the correct way to go for language redirects.

I have tested this item successfully on ae373fc

TEST OK

@infograf768 please check this.

Thanks for testing this and confirming that the pull request is functionally correct.

I am setting this to Needs Review so that the CMS maintainers can make a decision

301 is correct for multilang. This was changed in 3.4.

I have tested this item successfully on ae373fc

ok then

http://www.marketingchip.com/seo-experiments/how-does-a-303-redirect-affect-seo/

@brianteeman I would change this to RTC

Sorry thought I had :)

RTC

now the browser is caching the 301 redirects ... which means that if i change the default language the browser will not change it until the browser cache is cleared... isuppose that will happen to with search engines...

i still think making this redirect a 301 (that by default caches the redirect in the browser) is a choice that has problems.

Although it seems we can have 301 without caching. See http://stackoverflow.com/questions/12192590/how-to-do-a-non-cached-301-redirect/19003320#19003320

@infograf768 please reavaluate this.