Mastodon Instances

Mastodon Instances (instances.social) is a service for discovering Mastodon server instances. Its API allows developers to search for instances by criteria including language, user count, and stability, and to retrieve metadata about specific instances.

Mastodon Instances publishes 3 API contracts indexed on the APIs.io network, including Versions API, and 2 more. Tagged areas include Fediverse, Mastodon, Search, and Social.

The Mastodon Instances catalog on APIs.io includes 1 Spectral governance ruleset.

Mastodon Instances’ developer surface includes authentication, developer portal, signup flow, and 6 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

27.8/100 thin ▬ flat Agent 23/100 agent aware Front door AI 1/6 silent saas Full breakdown ↓
scored 2026-11-13 · rubric v0.28.0 · Show this score on your site →

AccessFreemiumSelf serve⚡ Free to try

1 published contract

Fediverse Mastodon Search Social

Kin Score

Kin Score How this is scored →
scored 2026-11-13 · rubric v0.28.0

Composite quality — 27.8/100 · thin

Contract Quality 9.6 / 21

Developer Ergonomics 5.3 / 17

Access Clarity 2.9 / 17

Operational Transparency 0.8 / 11

Contract Governance 1.4 / 10

Discoverability 4.9 / 9

Regulatory Posture 0.9 / 15

Agent readiness — 23/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 6 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 4 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

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/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship Ask about this →
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes Ask about this →
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0 Ask about this →
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link Ask about this →
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document Ask about this →
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented) Ask about this →

6 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Access Clarity scores 17.0 — up to +16.6 composite points Ask about this →
Developer Ergonomics scores 31.0 — up to +13.8 composite points Ask about this →
Contract Quality scores 45.3 — up to +13.7 composite points Ask about this →

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/mastodon-instances/apis.yml: open an issue on github.com/api-evangelist/mastodon-instances to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

OpenAPI

measured — observed by APIs.io (published)

APIs 3

Individual APIs this provider publishes, each with its own machine-readable definition.

Mastodon Instances API

The instances.social API allows searching for and retrieving information about Mastodon server instances, including user counts, language, software version, and uptime statistics.

Mastodon Instances API

The Instances API from Mastodon Instances — 4 operation(s) for instances.

Mastodon Instances Versions API

The Versions API from Mastodon Instances — 2 operation(s) for versions.

Open Collections 3

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Mastodon Instances API

OPEN COLLECTION

Mastodon Instances Versions API

OPEN COLLECTION

Mastodon Instances API

OPEN COLLECTION

Mastodon Instances API pricing

Not yet checked against Mastodon Instances's own pricing page. Compiled by API Evangelist on 2026-05-04; confirm before you rely on a figure. A free plan or tier is listed.

Plan	Price
Free freemium	Free
Professional paid	Free
Enterprise enterprise	—

Plan details, limits and sources →

Rate limits

Free Tier Default: 10 requests per minute
Free Tier Monthly Quota: 1000 requests per month
Professional Tier Default: 100 requests per minute

Compiled by API Evangelist, not yet checked against Mastodon Instances's documentation. All 5 limits →

Pricing Plans 1

Published pricing tiers and plan structures.

Mastodon Instances Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Mastodon Instances Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Mastodon Instances Finops

FINOPS

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs. Counts are the severity each rule declares, not results of running them.

Mastodon Instances API Rules

43 rules · 41 error-severity 1 warn-severity 1 info-severity

SPECTRAL

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Mastodon Instances Authentication

http · 1 scheme

SECURITY

Mastodon Instances Domain Security

TLSv1.3 · HSTS · DNSSEC

SECURITY

Agentic Access (API Evangelist recommendations) 1

Recommended x-agentic-access execution contracts for AI agents.

Mastodon Instances Agentic Access

6 operations

6 operations · 0 acting

AGENTIC

Resources

Get Started 2

Portal, sign-up, and the first successful call

Portal

Portal

Signup

Signup

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Authentication

Authentication

Operate 1

Status, limits, changes, and where to get help

RateLimits

RateLimits

Commercial 2

Pricing, plans, and the legal terms of use

Plans

Plans

FinOps

FinOps

Company 1

The organization behind the API

Website

Website

Source (apis.yml)

aid: mastodon-instances
name: Mastodon Instances
description: Mastodon Instances (instances.social) is a service for discovering Mastodon server instances. Its API allows
  developers to search for instances by criteria including language, user count, and stability, and to retrieve metadata about
  specific instances.
type: Index
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: freemium
  onboarding: self-serve
  trial: false
  try_now: true
  public: false
  gated: none
  gated_source:
  - onboarding
  label: Freemium · Self-serve signup
  confidence: medium
  source:
  - plans
  - authentication
  - security
  generated: '2026-11-13'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/mastodon-instances.png
url: https://raw.githubusercontent.com/api-evangelist/mastodon-instances/refs/heads/main/apis.yml
tags:
- Fediverse
- Mastodon
- Search
- Social
created: '2024-12-02'
modified: '2026-09-16'
specificationVersion: '0.23'
apis:
- aid: mastodon-instances:mastodon-instances
  name: Mastodon Instances API
  tags:
  - Mastodon
  - Search
  - Social
  humanURL: https://instances.social
  baseURL: https://instances.social/api
  properties:
  - url: https://instances.social/api/doc/
    type: Documentation
  description: The instances.social API allows searching for and retrieving information about Mastodon server instances, including
    user counts, language, software version, and uptime statistics.
- aid: mastodon-instances:mastodon-instances-instances-api
  name: Mastodon Instances API
  description: The Instances API from Mastodon Instances — 4 operation(s) for instances.
  humanURL: https://instances.social
  baseURL: https://instances.social/api
  tags:
  - Instances
  properties:
  - type: OpenAPI
    url: openapi/mastodon-instances-instances-api-openapi.yml
- aid: mastodon-instances:mastodon-instances-versions-api
  name: Mastodon Instances Versions API
  description: The Versions API from Mastodon Instances — 2 operation(s) for versions.
  humanURL: https://instances.social
  baseURL: https://instances.social/api
  tags:
  - Versions
  properties:
  - type: OpenAPI
    url: openapi/mastodon-instances-versions-api-openapi.yml
common:
- type: Plans
  url: plans/mastodon-instances-plans-pricing.yml
- type: RateLimits
  url: rate-limits/mastodon-instances-rate-limits.yml
- type: FinOps
  url: finops/mastodon-instances-finops.yml
- type: Website
  url: https://instances.social/
- type: AgenticAccess
  url: agentic-access/mastodon-instances-agentic-access.yml
- type: DomainSecurity
  url: security/mastodon-instances-domain-security.yml
- type: Authentication
  url: authentication/mastodon-instances-authentication.yml
- type: Portal
  url: https://instances.social
- type: Signup
  url: https://instances.social/api/token
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

Mastodon Instances API — frequently asked questions

Does Mastodon Instances have an API?

Yes. APIs.io lists 3 APIs from Mastodon Instances, including Mastodon Instances API, Mastodon Instances API and Mastodon Instances Versions API.

Is there an OpenAPI specification for the Mastodon Instances API?

Yes. APIs.io indexes 2 OpenAPI specifications for Mastodon Instances, each linked for download from this page.

How do I authenticate with the Mastodon Instances API?

Mastodon Instances uses bearer-token authentication (http · 1 scheme). The details are profiled on APIs.io as Mastodon Instances Authentication.

How much does the Mastodon Instances API cost?

APIs.io lists 3 pricing plans for Mastodon Instances, with each plan's price, limits and inclusions under Pricing on this page.

Is the Mastodon Instances API ready for AI agents?

Mastodon Instances has a Kin Score of 27.8 out of 100 (thin) and an Agent Readiness score of 22.7 (agent-aware), scored by API Evangelist on 2026-11-13.

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