How decide Google about duplicate content

Good question. I also want to know. This question will shut up mouth of many expert warriors. LOL.

If someone has stolen your information but if google crawled that person's site first then your site content be consider as duplicate content. So you need to provide content in such a way that it be found first by google. And for that you need to place relevant title that people and search engine can found it easily.

It entirely depends on crawling of websites. if Google found someone's website first and crawl his site person then your site consider as duplicate content. Whatever google find first mark as original content

Google considers domain age of the site in finding out duplicate content, I think so.

Content which get indexed first will be declared as duplicate content.

Google also considers a few other factors to decide original author of the content. Authorship markup is one other good way to tell the Google about the original author of the content.

I think everyone is misunderstanding what duplicate content penalty is?

Duplicate content penalty is for duplicate content within the same domain, not for content that is also on another site.

So the same article accessible through more than one URL on your domain is not good. The same article on another domain will not trigger a penalty.

Google will serve the most relevant, most linked to and therefore best quality result which might not be yours, but it won't penalise you for a copy of your article being elsewhere on the internet.

I just wrote an article about what to do when your content is stolen. Everything to do is in this article. Since I can't post a link here, go to HubPages, search for Writer Fox and find the article "Content Theft."

Here's the link to the article about Duplicate Content:
Duplicate Content by Writer Fox

There is a lot of opinion in this thread and very little fact. Ant B is the only guy to come up with something factual rather then something he read on a forum.

When google looks for duplicate content, it is looking for clear cases of abuse, such as ten duplicate pages within the same domain all littered with repeat keywords, over and over.

If it was to go on domain age then what's to stop me doing this -

1, you're my competitor

2. I pick up an expired 1997 domain with a PR of 3 or higher.

3. I fill up with a carbon copy of your content.

You get whacked by Google?

Multiple sites:

If it was based on the same text across multiple sites - then thousands of very valid news sites which rely on aggregate suppliers such as reuters would disapeer in SERPS. Religious sites that heavily quote the bible or quaran, would disapeer and be penalised. Sites which report on sports scores would all disapeer.

I could keep going, but I am sure you get the picture.

i usually just pray to god if my fresh content get stolen...

Straight answer to your question.Second site will be punished and the factors that make to do so are the indexing time and site quality.

Some of my stolen articles are outranking the original article I wrote. It really pisses me off because Google suppose to hate duplicate content!

I need to start sending cease & desist letters, me thinks.

I think Google might look for quality signals to identify the original content among duplicate ones. They are like link information, creation date, some form of page scoring, anchor text information, popularity information and age of website producing the content. I hope this helps, thanks.