Bambarbia Kirkudu

Independent Consultant (Toronto, Canada) specializing in Lucene, Hadoop, HBase, Nutch, SOLR, LingPipe, GATE, Data Mining, Search Engines, WebLogic, Oracle, Liferay Portal, Java, J2EE, SOA, and more. Master in MATH, Moscow State University n.a.Lomonosov

Thursday, May 10, 2007

 

What is 301 Redirect?

Can I use multiple redirects, and what happens indeed... from The Robot viewpoint:

URL1 (HTTP 301)-> URL2 (HTTP 301)-> URL3 (HTTP 200 Ok)-> The Page

The Page will be indexed.
URL1 or URL3 will be associated with a Page, depends on how Google implements their algorithms.

1. URL1 <-> Page
Pros: do not need to handle Session IDs for dynamic sites (which use redirect if browser does not support session cookies)
Good for: in-site (constrained) crawl (only internal redirects)
Cons: bad for external redirects; easy to steal content and PR from any site

2. URL3 <-> Page
Pros: good to prevent stealing of external content; can penalize URL1
Cons: bad for internal redirects (session IDs, moved pages, etc.)

I believe this is obvious, and Google follows the same logic. Unfortunately some other spiders do not follow 301/302 at all.

And each algorithm has some constraints like as:
- limit of redirects = 10 (some programming frameworks have default setting 100)
- throw away circular redirects

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