301 redirect and duplicate content

[rowtc2]

I have 10.000 url indexed by google.
I change the url of these pages in a new url structure.
I will put in htaccess redirect 301 from old url to new url.

When Google will index the new url will find a page identical with another one (the old url) and this is duplicat content. Because i am not sure he will find first the old url to be redirected to the new one.

How do you think is good to proceed ?

[tedster]

Duplicate content is only a filter to show just one url in the search results; it's not a penalty.

There is no worry about duplicate content when you use a 301 properly. The old url gets dropped from Google's index. And until it does go away, if Google is still showing it in the results, your traffic will still find the right page even though the new url is not yet showing.

You may find more help in this thread:
Changing URL Structure - take on tasks in a logical order [webmasterworld.com]

It is one several good discussions in the Hot Topics area [webmasterworld.com], which is always pinned to the top of this forum's index page.

[rowtc2]

I am thinking to make a sitemap for all the site before 301 redirect. After i put 301 redirect code in htacces and i modify url old structure to the new one , i will submit sitemap in WMT and Google will follow old links to new links and will refresh their index.
What do you think , is good to do this ?

[tedster]

I think the best approach would be to submit a sitemap that contains only the updated urls. Let Google use the crawl budget for your site mostly to get the new urls in the index - they will find the 301s naturally in any case.

[rowtc2]

I have old sitemap submited and WMT says: to many urls submited wirh 301 redirect. I have deleted old sitemap. I didn't submited a new sitemap.I have decided to wait Google crawling to see what is happening.

I see new urls start to appear naturally in Google index -is a good thing.