Introduction to Signatures

This topic explains what Signatures are and how they are used by Classwize's Rules tool.

What are signatures?

Signatures form the basis for allowing or filtering traffic within the school network. Signatures can be websites, applications, games, search keywords, IP addresses, ports, and groups of websites and third-party content.  

Types of signatures

These are the most common types of signatures that you’re most likely to see:

WebsiteA website signature is a web domain or subdomain. Applying a rule to a website signature will affect all URLs in that domain or subdomain.
GroupGroup signatures are usually created when a website or application requires one or more commonly blocked sites and services to work.
CategoryA category signature is a collection of related websites and services.  A website can be assigned to one or more categories, and a category can be a parent category or a child category (i.e. subcategory).

Website signatures

Website signatures refer to website domains and subdomains. A domain is a website’s name and is what follows the  “@” in an email address. It comes with an extension, such as  “.com”, “.net”,  “.org” and others in a URL. Thus you have:




A subdomain is a section of a domain and within a website, it serves as a way to organize navigation or create sections. It is possible to create multiple subdomains under one domain.  

IMPORTANT: A domain is different from a URL, which is the complete web address of a web page or online content. 

When we talk about websites being signatures, we’re usually talking about domains and subdomains, not individual URLs. Using a website signature will result in allowing or blocking  all of the individual pages in that website.  

For example, setting an Allow rule for the YouTube Website signature will let the students access every single video on YouTube. Blocking the Wikipedia Website Signature will stop students from accessing all Wikipedia pages.

Group signatures

Most websites need other websites in order for them to work properly. Sometimes with very popular websites, we create one Signature that includes a combination of the website and online content that are hosted by services that may be blocked in School Manager. This combination is called a group signature. 

For example, Khan Academy uses YouTube to host its videos. If you Allowed Khan Academy but had Blocked YouTube, Khan Academy wouldn’t work properly for your students. We combine Khan Academy and YouTube together into one group signature, so that videos will still load if you Allow Khan Academy but not YouTube.

Category signatures

Using a category signature is an efficient way to organize websites and create filtering rules that apply to all sites based on that classification. These are some of the ways that the Category signature works:

  1. The category signature allows schools to classify websites into one or more categories and create rules that apply to every single website in that category. This is the most common way to use categories in filtering rules. For example, instead of blocking sites one by one, you can simply check for their category and create a rule to block that category.  See Checking the Category of a Site

  2. Categories can contain other categories.  These are called parent and child categories.  For example, there’s a very broad parent category called Gaming.  This category contains several child categories: Online Gaming, Board and Card Gaming, and Video Games.  Each of those child categories contain Signatures.  

  3. You can set rules on parent and child categories, as well as individual signatures. This gives you more flexibility in making and applying rules.  You can create a rule that applies to the parent category, and then create exceptions by applying a different rule to another or child category, or an individual signature.

In the following example, is a website signature and is also assigned to  Social Media, and Internet and Telecom categories.  Although School Manager allows Tumblr as an Internet and Telecom site and is its own website signature, it is still blocked for falling under the Social Media category. 

website category/signature check

Other signatures

In addition to the top signatures mentioned above, School Manager also has the following minor signatures which you can still encounter when you create filtering rules. 

Application signatures

An application signature is a collection of all the websites, connections and ports needed to allow an application or service to connect to internet services on different types of devices. This is most commonly used for streaming services and multi-platform games like Fortnite, Among Us, Netflix or Amazon Prime.

Game signatures

We’re not saying it’s hard to stop kids from playing Among Us, but… it’s hard to stop kids from playing Among Us, or Fortnite, or Roblox or whatever other game is the current flavor of the month.  There are often multiple ways to access these games, and so we create specialized Game signatures that let you block—or allow— those games everywhere they can be played.