We've checked several English websites that claim to tell you if your website works in China but none seemed to provide an accurate answer.
Here's a more accurate way to see if your website is blocked in China:
http://ce.cloud.360.cn/ is a website that checks your website loading speed in different parts of mainland China and also Hong Kong and Taiwan. If your website loads in Hong Kong and Taiwan but not in other parts of China then it means that your website is blocked in China. Hong Kong and Taiwan have different internet rules from mainland China.
Example: A quick check of google.com revealed that it only loads in Hong Kong (香港) and Taiwan (台湾). The green colour means the website works in those areas (fast loading speed). The red colour means that the website doesn't load in those areas.
快 means fast loading speed
慢 means slow loading speed, usually it means the website doesn't load in those areas.
A quick check of baidu.com reveals that it's available in most areas of mainland China. The grey regions are not supported by http://ce.cloud.360.cn hence there are no statistics in those areas.
Below is a quick test of a random foreign website. When we were travelling in Shanghai and Guangdong, this website worked perfectly fine. If the map shows that the website loads in two or more provinces in mainland China (except Taiwan and Hong Kong) then it usually means the website is available in most areas of China.
We hope this is useful and please feel free to get in touch if you have any questions!