What referrer is shown in http request when google crawler visit a page?

[max.favilli]

Is it legit to show different content to http request having different referrer?

case a: user view one page of the site with plenty of information about one brand, and click on a link on that page to see a product detail page of that brand, here I don't want to repeat information about the brand itself

case b: a user view directly the product detail page clicking on a SERP result, in this case I would like to show him few paragraph about the brand

Is it bad? Anyone have experience in doing it?

My main concern is google crawler. Should not be considered cloaking because I am not differentiating on user-agent bot-no-bot.

But when google is crawling the site which referrer will use? I have no idea, does anyone know?

When going from one link to another on the website, is google crawler leaving the referrer empty?

[max.favilli]

After googling about it and thinking better I choose not too. I think you are absolutely right, too inconsistent.

[Highland]

You won't get a referrer. Googlebot is not like a real user, surfing from site to site. What Googlebot does is this (more or less)

1. Googlebot requests a standalone page
2. Googlebot parses the page out. During this process it notes the links on that page and, depending on various mechanisms (nofollow, internal page rank, the mood of Matt Cutts, etc) it will note those links for the system to parse later
3. Googlebot is done so it grabs another page off the page list (likely without know how it got on said list) and goes back to #1

Now, to your question. Since Googlebot has no referrer it won't get your alternate content. This means that your alternate content page won't get indexed.

I would suggest here that a best practice is NOT to filter on referrer data, which can be inconsistent and potentially fake. Instead, I would make a separate page that contains your extra data and allow users to decide if they want more information Thus Googlebot finds all your content and your users get a better experience.