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Posted: 29 December 2014
Updated: 30 April 2018

Blocked or not? Webapp that checks where your URL is censored

Stack Exchange

Question from Software Recommendations on Stack Exchange:

I maintain an app which uses several websites for documentation, data, community, etc.

I often hear that an URL or another is blocked in a country or another, typically China.

Is there an app similar to http://www.greatfirewallofchina.org but which would check in as many countries as possible? Possibly with different ISPs, as someone blocks are different.

My answer

[Read, comment, and vote on my answer at Stack Exchange]

Unfortunately, an application that does exactly what you want is technically impossible. There are ways to approximate what you want, however, and the more money and/or time you invest, the closer you will get to your goal.

There are a few reasons why it your request is impossible. Start by looking at the tool you mentioned and test a website. Notice that the tool tests to see if a website is blocked by trying to access the website from computers inside China. The only thing you know from that test is that those five computers were able to access the website at the time you asked.

When I lived in Beijing, very few websites were blocked all of the time. I could access Wikipedia, for example, about half the time. Furthermore, many websites were only partially blocked. I could usually access Google, but if I searched for some keywords, then the search would mysteriously time-out.

The issue is that censorship in most countries is rarely centralized and is usually secretive. When Turkey blocked Twitter, it was unusual that they announced they were blocking Twitter. Said differently, unlike spammer blacklists, censorship lists are rarely public.

Consider when Egypt cutoff most external internet access. The orders were all given by phone or in person, so no official censorship list existed. Furthermore, one of the ISP backbone providers was not disabled, so some traffic could go in and out of Egypt. It was censorship, but it wasn’t targeting any one website.

Even though no program could possibly do what you are asking, there are ways to approximate your goal. Uptime monitors located around the world are your best option.

https://www.uptrends.com/tools/uptime is a free tool that checks your server from 131 locations around the world. The problem is that it is not automated: you have to manually run the check yourself from time to time. If you are willing to pay, they offer the same service but automated.

I would offer some other ideas, but since they would require you to do some research on your own, I am afraid the moderators will delete my entire answer: and that would dissuade me from answering any more questions on this otherwise great forum.

Good luck!

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