Cat Facts is a free, no-authentication community REST API at catfact.ninja that serves random cat trivia and a catalog of cat breeds. It exposes three documented endpoints — a single random fact, a paginated list of facts, and a paginated list of breeds — and ships a Swagger UI based OpenAPI 3.0 document at /docs. The service is widely used in API onboarding tutorials, demos, and sample apps because it requires no API key and returns small, predictable JSON payloads.
Cat Facts (catfact.ninja) publishes 2 APIs on the APIs.io network: Breeds API and Facts API. Tagged areas include Animals, Cats, Trivia, Public APIs, and Community.
The Cat Facts (catfact.ninja) catalog on APIs.io includes 1 JSON-LD context and 2 Spectral governance rulesets.
Cat Facts (catfact.ninja)’s developer surface includes authentication, tooling, and 12 more developer resources.
Regulatory Posture applies to this provider. Its tags matched the
Horizontal (data, software, accessibility, platform) regime, so
Regulatory Posture carries 15 points of the composite.
If this regime is wrong for your business, say so on your
provider repo — the
applicability map is public and we will correct it.
Create-or-Update Ergonomics does not apply to this provider. The published contracts declare
no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's
denominator entirely — not scored zero. A reference or data API is not deficient for being unable to
upsert.
The six quality facets above are damped to 85 points between them,
because the conditional facet above carries the other
15. That is why each facet's contribution is shown against a damped
maximum: raising a quality facet moves the composite by 85% of its nominal
weight, not 100%. The full arithmetic is at apis.io/rating/.
aid: cat-facts-catfact
name: Cat Facts (catfact.ninja)
description: Cat Facts is a free, no-authentication community REST API at catfact.ninja that serves random cat trivia and
a catalog of cat breeds. It exposes three documented endpoints — a single random fact, a paginated list of facts, and a
paginated list of breeds — and ships a Swagger UI based OpenAPI 3.0 document at /docs. The service is widely used in API
onboarding tutorials, demos, and sample apps because it requires no API key and returns small, predictable JSON payloads.
url: https://catfact.ninja/
deliveryModel:
model: unknown
open_source: false
commercial: false
callable_host: true
label: Delivery model not determined — needs a product licence on record
confidence: low
source:
- openapi
generated: '2026-08-28'
method: derived
accessModel:
pricing: unknown
onboarding: open
trial: false
try_now: false
public: true
label: Open access
confidence: medium
source: []
generated: '2026-07-22'
method: derived
image: https://catfact.ninja/docs/asset/favicon-32x32.png
specificationVersion: '0.23'
created: '2026-05-28'
modified: '2026-05-30'
x-source: public-apis/public-apis
x-type: opensource
x-category: Animals
x-tier: 3
x-tier-reason: bulk-registered-from-public-apis
tags:
- Animals
- Cats
- Trivia
- Public APIs
- Community
- No Authentication
- REST
apis:
- aid: cat-facts-catfact:cat-facts-catfact-breeds-api
name: Cat Facts (catfact.ninja) Breeds API
description: Catalog of cat breeds with country, origin, coat, and pattern.
humanURL: https://catfact.ninja/
tags:
- Breeds
properties:
- type: OpenAPI
url: openapi/cat-facts-catfact-breeds-api-openapi.yml
- type: Documentation
url: https://catfact.ninja/
- type: SwaggerUI
url: https://catfact.ninja/
- type: OpenAPISource
url: https://catfact.ninja/docs?api-docs.json
- aid: cat-facts-catfact:cat-facts-catfact-facts-api
name: Cat Facts (catfact.ninja) Facts API
description: Random cat trivia, individually or in paginated lists.
humanURL: https://catfact.ninja/
tags:
- Facts
properties:
- type: OpenAPI
url: openapi/cat-facts-catfact-facts-api-openapi.yml
- type: Documentation
url: https://catfact.ninja/
- type: SwaggerUI
url: https://catfact.ninja/
- type: OpenAPISource
url: https://catfact.ninja/docs?api-docs.json
common:
- type: AgenticAccess
url: agentic-access/cat-facts-catfact-agentic-access.yml
- type: DomainSecurity
url: security/cat-facts-catfact-domain-security.yml
- type: Website
url: https://catfact.ninja/
- type: SwaggerUI
url: https://catfact.ninja/
- type: OpenAPI
url: https://catfact.ninja/docs?api-docs.json
- type: ContactEmail
url: mailto:contact@catfact.ninja
- type: PublicAPIsListing
url: https://github.com/public-apis/public-apis
- type: Authentication
title: No Authentication Required
url: https://catfact.ninja/
- type: Tools
title: MCP Server (Community — cursethevulgar)
url: https://github.com/cursethevulgar/catfact-mcp-server
- type: Tools
title: MCP Server (Community — mtrmarko)
url: https://github.com/mtrmarko/cat-facts-mcp
- type: Tools
title: MCP Server (Community — Volspan)
url: https://github.com/volspan-deployments/cat-facts-mcp
- type: SpectralRules
url: rules/cat-facts-catfact-rules.yml
- type: Vocabulary
url: vocabulary/cat-facts-catfact-vocabulary.yml
- type: JSONLDContext
url: json-ld/cat-facts-catfact-context.jsonld
features:
- name: Free and Open
description: No API key, no signup, no quota header. Anyone can hit catfact.ninja and start getting JSON back. Ideal for
first-class onboarding examples in tutorials and SDK quickstarts.
- name: Paginated Listings
description: The /facts and /breeds endpoints return Laravel-style paginated responses with current_page, last_page, per_page,
total, and a links array suitable for "next/prev" UI patterns.
- name: Length-Filtered Facts
description: Both /fact and /facts accept a max_length query parameter, letting clients restrict trivia length for SMS-friendly,
push-notification-friendly, or banner use cases.
- name: Self-Describing OpenAPI
description: A live OpenAPI 3.0 document is published at /docs?api-docs.json and rendered as Swagger UI at /docs — usable
directly by codegen tools, Postman import, and AI agent toolkits.
useCases:
- name: API Onboarding Tutorials
description: Used in countless "hello-world" REST tutorials because it returns small JSON, requires no auth, and is CORS-friendly.
A canonical first call for browsers, mobile apps, and SDKs.
- name: SMS and Chatbot Daily Facts
description: The original Cat Facts service became a meme around texting friends a daily cat fact. catfact.ninja is the
easiest backend for any "daily fact" bot, including SMS, Discord, and Slack integrations.
- name: Load Testing and Demo Apps
description: Engineering teams point load generators, screen-recording demos, and observability sample apps at catfact.ninja
because it tolerates traffic, returns tiny payloads, and never requires credential rotation.
- name: MCP and Agent Tool Demos
description: Several community Model Context Protocol servers wrap catfact.ninja as a "hello world" tool because the surface
is small, safe, and read-only — perfect for showing Claude using a tool.
integrations:
- name: Public APIs Index
description: Listed in the popular public-apis/public-apis index as a free, no-auth Animals API.
- name: Community MCP Servers
description: At least three community-built MCP servers wrap the catfact.ninja endpoints as Claude tools.
- name: Swagger UI
description: Ships a live Swagger UI at https://catfact.ninja/ that imports the OpenAPI spec from /docs.
solutions:
- name: Lowest-Friction Demo API
description: When you need a public, free, no-auth REST API to demo SDK generation, OpenAPI tooling, mock servers, or agent
tool calls, catfact.ninja is the smallest acceptable surface area.
maintainers:
- FN: Kin Lane
email: kin@apievangelist.com
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