How does JS0 Index work?

Have you ever wondered what tool a website is built with or where its server is located? All this information is just a click away with JS0 Index. With this service, we want to make it easier for end users and companies to gather information about websites and better evaluate them. Even simple aspects like the SSL certificate or the software used can give information about the web developer's skills. Subsequently, all available means for data collection are listed.


While generating the report, JS0 Index tries to match the web page with over 10000 patterns to detect software like CMS, CDN, Javascript libraries etc. Usually the results are very accurate. However, there are cases when this algorithm is wrong. If software does not make sense at this point, check it on the website itself or contact us so we can check it manually and adjust our algorithm if necessary. The code is based on the open source library Wappalyzer. In addition to this, other technology lookups have been added.

IP Lookup

Our IP data is based on our own freely available service With the help of this, IP addresses can be identified per location, company or AS etc.. It is available as a free API without limitation or as a complete database for download. (More information on the own project homepage). The data is regularly maintained and goes beyond most other services as it also contains e.g. the website of the company as well as abuse contacts. The project is also based on donations. If the database could help once, consider donating a small amount... :)

SSL Certificate

An SSL certificate is almost indispensable in today's Internet. Often the certificates are issued directly by the provider of the website or a large certification authority. Certificates also differ into three main types. Extended validation, organization validation and domain validation. All three have advantages and disadvantages, especially in terms of price and trustworthiness. While large companies rely on extended validation certificates that usually cost over $10k per year, a simple website can use a domain validation certificate that is available for free from companies like Let's Encrypt. This does not affect the trustworthiness of the website. Especially when Google announced that websites without SSL certificates will no longer appear in Google search, there are almost no 'unsafe' websites for the normal consumer. Otherwise, its shown in this section of the report.


A WHOIS (Who is) database can be used to locate various information about a domain name. This includes company, registration date, contact, etc. However, the information can vary greatly by TLD (Top Level Domain). Therefore, an analysis of the different information is only possible to a very limited extent. In addition, some countries like Switzerland have already switched to a new protocol called RDAP, which makes the query even more difficult. Point of view now WHOIS information is displayed only in a RAW format. However, this will change with a later update.


For a long time, the ranking of websites was dominated by Alexa. However, this service was shut down. JS0 Index therefore relies on the freely available provider DomCop. Websites are assigned a global rank every three months with the help of DomCop. This is based on various factors such as search engine ranking, number of hits, etc. and often very accurately reflects the popularity of the searched website. In addition, a 'Pagerank' score is available from DomCop. This indicates how well a website has been optimized for search engines. Measured here are mainly the call time, responsiveness and size of the content. This service was founded because Google switched off Pagerank at the end of 2010 and there was no comparable service currently available.


DNS is one of the most important protocols on the Internet. Besides, it is the most informative. The Domain Name System is like a phone book that stores all the information about a website and connects visitors to the appropriate backend. Thus, not only all providers for the website itself can be read, but also providers for email, verification and other services that are not accessible via the HTTP protocol.