Freedom League Standard Notation is a system by which alternate dimensions can be categorized. First codified by Doctor Atom in the 1960s,Standard Notation replaced the previous scheme of merely giving each new alternate world a nickname based on its main differentiating feature. Atom realized that as dimensional science became more advanced and more dimensions were explored, a finer-grained system would be required. All dimensions that have been visited by the Freedom League or their allies have a designation in Standard Notation. Standard Notation is based on establishing four major facts about each universe and assigning descriptors for each in the form of a word, letter or number. There are a number of optional descriptors that can be appended in special circumstances as well.

The first step in the designation process is nomenclature. For purposes of ease during the era in which the system was put into effect, the default nomenclature is Earth, for any universe where the planet Earth is present and English is a major language. If another language has arisen on that world to supplant English as a major language, the name for Earth in that language will be substituted (i.e. Erde, Terre). In the rare event that a universe is found where the planet is entirely gone, or where all evidence of life has been obliterated so thoroughly that no cultural conjectures may be drawn, the designation Nihil will be substituted.

The second designator is that of a universe's habitability and safety for travelers and scientists. This is graded in alphabetical groupings, based on the condition of the planet, the presence of hostile forces, and the existence of dangerous circumstances. Designators should use the letter grouping that identifies the greatest danger present.

• A-F: These letters designate non-hostile Primelike worlds without contraindications for travel and exploration. Designations are based on a scale from most hospitable to least, based on factors like climate and overall pollution, with A being most pleasant and F not recommended for prolonged exposure.
• G-K: These letters indicate habitable universes with inhabitants who might prove hostile to some or all explorers and travelers. G indicates a generally peaceful population with a few specific triggers for hostility, while K indicates an entirely hostile populace who will prove a danger to any traveler.
• L-Q: These letters indicate universes with noticeable differences in the physical laws from Earth Prime. L indicates minor differences that may be more entertaining than troublesome, Q indicates differences so substantial that unsupported human life is endangered.
• R-V: These letters indicate universes with variations on Prime that might be expected to be mentally or psychologically distressing to many travelers and explorers. R indicates a universe that most would consider mildly disturbing, where V is likely to cause mental anguish to many travelers.
• W: This designator indicates a world that is so close to Prime as to be virtually indistinguishable.
• X: This designator indicates a planet that is unclassifiable for any reason. Care should be taken to explain this designation in the dossier, and recategorization should be a priority.
• Y: This designator indicates a universe that is inimical to human life by its very nature, but that is unlikely to create a danger outside itself. Travel to these universes should be avoided at all costs.
• Z: This designation indicates a universe that is inimical to human life by its very nature, and could also pose a danger to other universes. Travel to these universes must be strictly controlled, and information about them must be classified to avoid potential weaponization.

The third designator is a single-word explanation of the main distinctive point of the universe. This is inherently a matter of some subjectivity, but certain designators see frequent use. Ideally, care will be taken to avoid duplication of initial letters where possible. Official Standard Notation includes the entire word descriptor for Distinctiveness, but it will inevitably be shortened for easy reference. Where more than one descriptor might apply, choose the one that is most important for a traveler to be aware of.

Some common Distinctiveness descriptors include:

• Animal: A universe where sentient animals are the majority of the population.
• Disaster: A universe where Earth suffers from the effect of one or more extreme natural disasters or diseases.
• Eldritch: A universe in which magic has displaced science in its control of physical law.
• Gender: A gender-displaced or gender-reversed universe.
• Isolate: A universe that is unaware of its position in the multiverse, and/or with no close sister universes
• Malign: A universe with a pronounced moral inversion not inflicted from outside.
• Nazi: A universe where the Axis won World War II and continue to hold strong influence.
• Omega: A universe that has fallen under the influence of the Terminus.
• Retro: A universe where technology is substantially behind that of Prime, by choice or otherwise.
• Self: A universe where Earth suffers from extreme self-inflicted damage.
• Tech: A universe where technology is substantially advanced beyond that available on Prime.
• War: A universe in the grip of a world war that affects a majority of the population.

The fourth standard descriptor is merely a measure of uniqueness. Given the structure of the multiverse and the limits of any cataloging system, it is inevitable that there will be multiple worlds with the same descriptors. The Uniqueness number solves this problem by adding a number to the other descriptors indicating the order in which it was discovered. Therefore, the first time a set of descriptors is assigned, it will be given the Uniqueness descriptor 1. The next time that set of descriptors is assigned, the Uniqueness descriptor will be 2, and so on.

Some universes have special circumstances that require designators beyond the standard four. There are only a few occasions when these notations are appropriate. Special Notations are indicated in parentheses after the Uniqueness designator.

Some examples of special notation include:

• Allied: This universe is a special ally to the Prime Freedom League.
• Closed: This universe has requested no contact with other universes.
• Endangered: This universe has a Primelike population in imminent danger of extinction.
• Enemy: This universe is aware of and especially hostile to the Prime Freedom League.
• Extinct: This universe once harbored a Primelike population, but is now uninhabited.

It should be noted that Earth Prime does not follow the standard notation and may simply be referred to as Prime.

Some examples of worlds using Freedom League Standard Notation:

• Earth Z-Omega-1(extinct): The home dimension of Young Freedom member Wander, this dangerous and uninhabitable dimension is classified by the League.
• Earth-D-Self-7(extinct): Nicknamed Sanctuary, this extinct dimension is the headquarters of Fleur de Joie.
• Erde-J-Nazi-1(enemy): Commonly known simply as “Erde,” many heroes from Earth Prime have had dealings with this dimension.
• Earth-V-Malign-1(enemy): Commonly known as Anti-Earth, this universe is the most pronounced and well-known example of moral inversion.
• Earth-A-Gender-1: Also referred to as Earth-XX, this is a close Prime duplicate with the exception of complete gender inversion from the Prime population.
• Earth-N-Isolate-4 A recently encountered universe where all superpowers arise from a single source and have only existed since the early 1990s.