Almost all SCP files use some sort of Classification System to categorize SCP Objects. The exact details of how these classes are assigned can vary greatly depending on the article, but they pertain mostly to how the Foundation contains the SCPs and the complications that are involved in the process.
Traditionally, SCPs are assigned one of multiple different Objects Classes (sometimes called Containment Classes), which usually described the difficulty level of keeping the anomaly contained. Most SCP articles, especially before the Anomaly Classification System (ACS) was created, only assign a single Object Class for each anomaly. Post-ACS, most newer articles use either one or two Containment Classes: Primary and/or Secondary (also called Esoteric), plus a few additional categories.
Primary Classes
Common Classes
These are the three classic Object Classes, which are most commonly found in the vast majority of SCP articles.
• Safe- Safe-class SCPs are anomalies that are easily and safely contained. This is often due to the fact that the Foundation has researched the SCP well enough that the containment does not require significant resources or that the anomalies require a specific and conscious activation or trigger. Classifying an SCP as Safe, however, does not mean that handling or activating it does not pose a threat.
• Euclid- Euclid-Class SCPs are anomalies that require more resources to contain completely or where containment isn't always reliable. Usually this is because the SCP is insufficiently understood or inherently unpredictable. Euclid is the Object Class with the greatest scope, and it's usually a safe bet that an SCP will be this class if it doesn't easily fall into any of the other standard Object Classes. As a note, any SCP that's autonomous, sentient and/or sapient is generally classified as Euclid, due to the inherent unpredictability of an object that can act or think on its own.
• Keter- Keter-Class SCPs are anomalies that are exceedingly difficult to contain consistently or reliably, with containment procedures often being extensive and complex. The Foundation often can't contain these SCPs well due to not having a solid understanding of the anomaly, or lacking the technology to properly contain or counter it. A Keter SCP does not mean the SCP is dangerous, just that it is simply very difficult or costly to contain.
Other Object Classes
• Neutralized- Neutralized SCPs are anomalies that are no longer anomalous, either through having been intentionally or accidentally destroyed, or disabled.
• Thaumiel- Thaumiel-Class SCPs are anomalies that the Foundation specifically use to contain other SCPs. Even the mere existence of Thaumiel-Class Objects is classified at the highest levels of the Foundation and their locations, functions, and current status are known to few Foundation personnel outside of the 05 Council.
• Apollyon- Apollyon-Class SCPs are anomalies that cannot be contained, are expected to breach containment imminently, or some other similar scenario. Such anomalies are usually associated with world-ending threats or a K-Class Scenario of some kind and require a massive effort from the Foundation to deal with.
• Archon- Archon-Class SCPs are anomalies that could theoretically be contained but are best left uncontained for some reason. Archon SCPs may be a part of consensus reality that is difficult to fully contain or may have adverse effects if put into containment. These SCPs are not uncontainable - the defining feature of the class is that the Foundation chooses to not put the anomaly into containment.
Secondary/Esoteric Classes
The following Object Classes are Sub-Classes that supplement the object's primary (or former) classification. An Esoteric object is an SCP that doesn't fall into the previous categories.
Subclasses
• Suffix system
• Type system
• Objective/containment system
• Additional systems
Anomaly Classification System
ACS is a new template for classifying SCPs, which adds other categories to supplement the Object Classes (both Primary and Secondary).
