Introduction to Compression and SEO
Compression, in the context of search engines, refers to how much web pages can be reduced in size. This process is similar to shrinking a document into a zip file. Search engines use compression to save space and speed up processing times. It’s a common practice among all search engines.
How Search Engines Use Compression
Search engines compress indexed web pages to improve their efficiency. This compression helps search crawlers quickly access web pages, sending a signal to Googlebot that it won’t strain the server and it’s okay to index more pages. As a result, compression plays a significant role in ensuring that websites are crawled and indexed effectively.
Website Compression and Its Benefits
Websites and host providers also compress web pages, which is beneficial for several reasons. Compression speeds up websites, providing users with a high-quality experience. Most web hosts enable compression by default because it’s good for websites, users, and hosts, as it saves on bandwidth loads. This mutual benefit is why compression is widely adopted across the web.
The Relationship Between Compression and Spam
Research conducted in 2006 by Marc Najork and Dennis Fetterly, two leading researchers, discovered that highly compressible web pages often correlated with low-quality content. The study, titled "Spam, Damn Spam, and Statistics: Using Statistical Analysis to Locate Spam Web Pages," found that 70% of web pages with a compression level of 4.0 or higher tended to be low-quality pages with redundant word usage. The average compression level of normal sites was around 2.0.
Compression Ratios of Normal Web Pages
The research paper highlights the following averages for normal web pages:
- Compression ratio of 2.0: The most frequently occurring compression ratio in the dataset.
- Compression ratio of 2.1: Half of the pages have a compression ratio below 2.1, and half have a compression ratio above it.
- Compression ratio of 2.11: The average compression ratio of the pages analyzed.
Do Search Engines Utilize Compressibility?
It’s reasonable to assume that search engines might use compressibility as one of the signals to identify obvious spam. However, it’s also logical to assume that if search engines employ compressibility, they would use it alongside other signals to increase the accuracy of their metrics. The exact methods used by Google remain unclear.
The Challenge of Determining Google’s Use of Compression
Determining whether Google uses compression as a spam signal is challenging. If a site triggers the 4.0 compression ratio along with other spam signals, it likely won’t appear in search results. This means there’s no way to test and confirm whether Google is using compression ratio as a spam signal. The absence of such sites from search results could be due to various factors, making it impossible to prove or disprove the use of compression as a signal.
Conclusion
Compressibility may or may not be an SEO myth, but one thing is certain: it’s not something that publishers or SEOs of normal sites should worry about. Given that spam signals are not used in isolation due to the risk of false positives, and considering that triggering these signals requires abnormal levels of heavy-handed spam tactics, the average website does not need to worry about compression ratios. As long as a website provides quality content and doesn’t engage in spammy practices, compression ratios should not be a concern.