Citability Index
The Citability Index is a score from 0 to 100 that measures whether a website can be read, understood and cited by a generative model.
It is published by Primafonte, computed from 33 technical checks grouped into four weighted layers, and versioned: every report states which version produced it. This page defines the term. The methodology documents how each point is awarded.
What does the Citability Index measure?
It measures four things a model needs before it can name you as a source: that its crawler can reach you, that what the crawler sees matches what a person sees, that your content survives being cut into passages, and that you are identifiable as a specific entity rather than one more website.
Each one is a layer with its own weight, and the weights are not equal. What stops a model reading you at all counts for more than what merely shades how it describes you.
What does a score mean?
The number lands in one of four bands, and the band matters more than the digit. The distance between a 58 and a 61 is noise; the distance between two bands is whether a model can use you as a source at all.
- 0 to 39 — not citable: models cannot use the site as a source.
- 40 to 59 — partially readable: they find you, but cannot cite you reliably.
- 60 to 79 — citable with gaps: it works, with specific blind spots.
- 80 to 100 — ready: no structural blockers.
How is it different from an SEO score?
An SEO score predicts whether you will rank in a list of links. The Citability Index predicts whether a model can quote you inside a written answer, and the two reward different signals: a page can rank first on Google and still be unusable as a source, because its content only exists after JavaScript runs.
They share foundations and diverge on what they value. Domain authority moves rankings and does nothing for citability. A self-contained paragraph under a clear heading does the opposite.
Who publishes the Citability Index, and can a score be bought?
Primafonte publishes it, and Primafonte is maintained by Obsidiaan Tech S.L. Nobody pays to appear, to be measured or to change a score. The scan is free and the report is shown in full, with no signup and no email.
The work is funded by the implementation services bought by those who want the fixes done for them. That is the entire business model, and it is stated here because a measurement whose funding you cannot see is a measurement you cannot check.
Does the Citability Index change over time?
The method is versioned and every report carries the version that produced it. Thresholds move as evidence accumulates, and a check that cannot explain why it matters to a model is withdrawn rather than kept for the sake of the count.
Old scores are never recalculated. A report describes how a website stood on the day it was measured, under that day's criteria, which is why a difference between two reports from different versions is a change of criteria and not progress.
What is this definition built on?
The term is ours; the criteria behind it are not. These are the four references the engine implements literally, each one public and free to read in full.
- GEO: Generative Engine Optimization
The study that measured the effect of citing sources, supplying data and adding quotations: up to 40% more visibility in answers. Two of the content checks take their weight from it.
- schema.org
The vocabulary structured data is validated against. It is also what this page uses to declare the term itself as a defined entity rather than a phrase.
- RFC 9309, the Robots Exclusion Protocol
The standard that settles how a robots.txt is read, including that the longest pattern wins and that Allow wins a tie. The discoverability layer applies it.
- The llms.txt convention
The proposed Markdown index file for agents. It is a de facto convention and not a settled specification, which is why its weight in the index may change.
Frequently asked questions about Citability Index
Is the Citability Index an official standard?
- No. It is an open, versioned methodology published by Primafonte, not a standard issued by a standards body. The checks implement published specifications and one measured study, and the documentation names which, with what weight and what threshold, so that anyone can disagree with a specific number instead of with the whole.
Can I measure my own site without Primafonte?
- Yes. Every check is documented with its threshold and its weight, and the methodology is published under a Creative Commons Attribution licence. Doing it by hand takes hours rather than seconds, but nothing in it is secret, and that is deliberate: a score nobody can reproduce is a score nobody should trust.
Does a high Citability Index guarantee that AI will cite me?
- No, and a tool that promises otherwise is selling something. The index measures whether the technical and structural obstacles have been removed. Whether a model then names you depends on your category, your competitors and how each engine reindexes. It is a necessary condition, not a sufficient one.