SCP Foundation Classes: Containment Difficulty & Tier Guide - Guide

SCP Foundation Classes: Containment Difficulty & Tier Guide

Master SCP Foundation classes: difficulty levels, containment risks, and detailed breakdowns of Safe, Euclid, Keter, and Thaumiel tiers.

2026-07-25
scp morph Wiki Team
Quick Guide
  • Object Classes indicate containment difficulty, not danger level.
  • Safe SCPs are easily contained, while Keter require immense resources.
  • Thaumiel objects are used by the Foundation to contain other anomalies.
  • Esoteric classes like Apollyon represent uncontainable threats.
  • Primary classes determine resource allocation and research priority.

Understanding Object Classes

Object Classes serve as a standardized system within the SCP Foundation to categorize anomalies based on their containment requirements. These classifications are not measures of how dangerous an item is, but rather an indicator of how difficult it is to lock up. This distinction is crucial for resource allocation, budgeting, and research prioritization.

The vast majority of anomalies fall into the three primary classifications: Safe, Euclid, and Keter. However, the Foundation utilizes a variety of secondary and esoteric classes for unique or extreme scenarios.

Safe Class

  • Containment: Easy and reliable
  • Trigger: Often requires activation
  • Risk: Low if left alone

Euclid Class

  • Containment: Unpredictable
  • Behavior: Autonomous or sapient
  • Risk: Hard to predict

Keter Class

  • Containment: Extremely difficult
  • Cost: High resource usage
  • Risk: Hard to maintain
Important Note

Classifying an anomaly as "Safe" does not mean it is harmless. It simply means the Foundation can put it in a box and leave it alone without it escaping. A Safe SCP can still be lethal if activated improperly.

ClassDifficultyAutonomyResource Cost
SafeLowNoneLow
EuclidModerateHighModerate
KeterExtremeVariableHigh
ThaumielN/AHighVery High

The Big Three: Safe, Euclid, Keter

The Locked Box Test is the informal guideline researchers use to determine the appropriate Object Class. If you lock it in a box, leave it alone, and nothing happens, it is Safe. If you are unsure what will happen, it is Euclid. If it easily escapes, it is Keter.

1

Identify Containment Needs

Assess the resources required to keep the anomaly secured. Does it need a standard locker, or a complex multi-layered facility?

2

Evaluate Behavior

Determine if the object is autonomous, sapient, or predictable. Living entities are almost always at least Euclid class due to their needs.

3

Assign Classification

Apply the Locked Box Test. If the object requires constant attention or specific triggers to be contained, avoid the Safe label.

Pro Tip

Any SCP that is alive, autonomous, or sapient is generally classified as Euclid. You cannot simply lock a living being in a box without consequences, making them inherently unpredictable to contain.

CriteriaSafeEuclidKeter
Locked Box TestNothing happensUnsure what happensIt escapes
KnowledgeWell understoodInsufficiently understoodPoorly understood
Reliability100% reliableUnreliableContainment is complex

Secondary and Esoteric Classes

Beyond the standard three, the Foundation recognizes several Secondary Classes for specific containment scenarios. These are distinct from "Esoteric" classes, which are often unique to a specific narrative.

Thaumiel class objects are anomalies that the Foundation uses to contain other anomalies. Their existence is often classified to the highest levels, known only to the O5 Council. Conversely, Apollyon class anomalies represent uncontainable threats, often associated with world-ending scenarios that cannot be stopped.

Esoteric Definitions

Secondary classes like Archon and Cernunnos describe anomalies that can be contained but are not, either due to dire consequences (Archon) or ethical/logistical reasons (Cernunnos).

ClassDefinitionContainment Status
ThaumielUsed to contain other SCPsActive Foundation use
ApollyonUncontainable world-ending threatImpossible
ArchonBest left uncontainedTheoretical refusal
NeutralizedNo longer anomalousDestroyed or disabled
ExplainedDebunked or understood by scienceNone needed

Classification Checklist & Maintenance

Proper classification is not static. Anomalies can change classes as they are studied, destroyed, or better understood. Maintaining accurate records is vital for the safety of Foundation personnel.

Classification Review Checklist:

  • Verify the Locked Box Test results
  • Confirm if the anomaly is autonomous or sapient
  • Assess if current containment procedures are failing
  • Update status if anomaly is destroyed (Neutralized)
  • Review if new science explains the phenomenon (Explained)
Reclassification Protocol

If an SCP is fully understood by mainstream science or debunked as a hoax, it must be reclassified as Explained. If it is destroyed or its effects cease, it becomes Neutralized.

Old ClassNew ClassReason for Change
ActiveNeutralizedDestroyed or effects ceased
Any ClassExplainedScience debunks the anomaly
Any ClassDecommissionedIntentional destruction
PendingPrimary ClassResearch completed

Frequently Asked Questions

Q: Does a higher Object Class mean the SCP is more dangerous?

No. Object Classes strictly refer to the difficulty of containment, not the lethality of the anomaly. A Safe SCP can instantly kill you if you interact with it, while a Keter SCP might be completely harmless but impossible to keep in a box.

Q: What is the 'Locked Box Test'?

The Locked Box Test is a heuristic: If you lock it in a box and nothing happens, it is Safe. If you are unsure what will happen, it is Euclid. If it escapes easily, it is Keter.

Q: What are Thaumiel class objects?

Thaumiel class SCPs are anomalies that the Foundation utilizes to contain other anomalies. They are typically extremely powerful and their existence is a high-level secret.

Q: Can an SCP have more than one Object Class?

Generally, no. However, it is permitted to use a secondary class in addition to a primary one for tagging purposes, especially if the classification changes over time within the article's narrative.