Web robots, web crawlers, and web spiders, they refer to the same thing. Crawlers and spiders are automated scripts/programs that browse the World Wide Web in an automated, methodical manner. Web spiders also allow marketing firms to conduct competitive analyses, researchers to look up trends, search engines to index pages, and more. Although a wide range of legitimate sites utilize web spidering and crawling as a means of providing up-to-date data, there are some websites that still choose to block crawlers and spiders. Let’s find out why.
Sensitive Corporate Information
Online businesses want to reach their target customers without exposing any sensitive or competitive information to their competitors. If crawlers and spiders from competitors’ networks are discovered, the website can block this incoming traffic or even provide incorrect information.
Copyright Infringement and Legal Issues
Data found in some websites can only be viewed by a limited audience for legal reasons. With that in mind, these websites set restrictions that determine when the data can be accessed, how often it can be accessed, where it can be accessed from, etc. It is not recommended that these websites are accessed in an automated fashion as it can violate their terms of services (TOS). Remember, crawlers and spiders are part of automated systems.
Negative Impact on a Website’s Performance
Sometimes the load from automated systems such as web crawlers may have an undesirable impact on the overall performance of the target website. For example, long web page load times may make visitors leave the site, even before the page finishes loading.
Avoid Increasing Bandwidth Expenses
Website owners are usually required to pay a regular fee for bandwidth. If a web crawler causes the site to receive high traffic in a short period of time, the bandwidth charges can escalate pretty quickly. Since there is little an affected website can do to curb this problem, one of the ways is to block the IP address (there may be more than one) that is frequently visiting the site. It is important that one considers spreading his or her outgoing traffic via a larger pool of IP addresses and over a longer time period.
Some websites are natural targets for abuse. Good examples include web based email systems. To prevent their users from receiving spam emails, these websites choose to block crawlers and spiders. They even take measures to prevent automated access, such as implementing text message confirmation, CAPTCHAs, etc., to validate that a human is accessing the site.