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APIs · head to head

Asyncapi vs Windmill

Asyncapi logo

Asyncapi

APIs

Specification and tools for defining asynchronous APIs

From
Free
Rated
-
Full reviewWebsite
Windmill logo

Windmill

Automation Integration

Open-source developer platform for building scripts, workflows, and internal apps

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Asyncapi complex to implement and debug asynchronous operations due to their non-linear and concurrent nature; Windmill free self-hosted tier caps SSO users at 10 and workspaces at 3, requiring Enterprise for larger teams.
  • They diverge on capability: Asyncapi covers API Specification, Windmill covers Script-to-workflow engine.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which Asyncapi and Windmill actually diverge.

Attributes where Asyncapi and Windmill differ
AttributeAsyncapiWindmill
PlatformsWeb, CLI, IDE Extensionsweb, api, linux, windows, mac
CategoryAPIsAutomation Integration
Founded2019Unknown

Identical on both: starting price (Free), pricing model (open-source), free tier (Yes), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Asyncapi

  • API Specification
  • Code generation
  • Documentation
  • Multiple messaging protocols
  • Code generators
  • Specification support
  • Tools support
  • CLI support

Only in Windmill

  • Script-to-workflow engine
  • Auto-generated UIs
  • Self-hosted deployment
  • Git sync
  • SSO support
  • Audit logs

What people use each for

The jobs each tool is most often brought in to do.

Asyncapi

  • API Developmentnot Windmill
  • API Gatewaynot Windmill
  • API Testingnot Windmill
  • API Documentationnot Windmill
  • Microservicesnot Windmill

Windmill

  • Turning ad-hoc scripts into scheduled jobs and APIsnot Asyncapi
  • Building internal tools from existing Python/TypeScript codenot Asyncapi
  • Self-hosted automation for engineering teamsnot Asyncapi
  • Orchestrating multi-language workflowsnot Asyncapi

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Asyncapi

  • Complex to implement and debug asynchronous operations due to their non-linear and concurrent nature
  • Keeping AsyncAPI documents up to date is challenging as systems evolve
  • Tracing and debugging asynchronous operations is more difficult than synchronous request-response patterns

Windmill

  • Free self-hosted tier caps SSO users at 10 and workspaces at 3, requiring Enterprise for larger teams.
  • Compute unit and seat-based pricing (developer vs. operator seats, worker compute units) adds pricing complexity beyond a flat monthly fee.
  • Email triggers are capped at 100/day on the free tier, limiting event-driven use cases without upgrading.
  • Smaller ecosystem of pre-built integrations compared to more established automation tools like n8n.

Pricing, plan by plan

Asyncapi

Free
  • Open SourceFree
    • AsyncAPI specification
    • Tools
    • Community support

Windmill

Free
  • Free / Open-sourceFree
    • Unlimited executions
    • Self-hosted deployment
    • Max 10 users with SSO
  • Enterprise$120/month
    • Unlimited executions and workspaces
    • Uncapped SSO seats
    • 24/7 priority support (3-hour response)

Which should you pick?

Choose Asyncapi if

  • You need api specification.
  • You want to start without paying.
  • You work on Web, CLI, IDE Extensions.
  • You also want code generation.
Asyncapi review

Choose Windmill if

  • You need script-to-workflow engine.
  • You want to start without paying.
  • You work on web, api, linux, windows, mac.
  • You also want auto-generated uis.
Windmill review

Questions people ask

Is Asyncapi or Windmill better?
Neither clearly leads. Asyncapi starts at Free and Windmill at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Asyncapi or Windmill?
Asyncapi starts at Free and Windmill at Free.
Does Asyncapi or Windmill run on more platforms?
Asyncapi runs on Web, CLI, IDE Extensions. Windmill runs on web, api, linux, windows, mac.
Can I use Asyncapi for free?
Both have a free tier, so you can try either at no cost before committing.
What is Asyncapi best used for?
Asyncapi is most often used for api development, api gateway, api testing, api documentation. Of those, api development and api gateway are not what Windmill is typically brought in for.
What can Asyncapi do that Windmill cannot?
Asyncapi covers API Specification, Code generation, Documentation, Multiple messaging protocols. Windmill covers Script-to-workflow engine, Auto-generated UIs, Self-hosted deployment, Git sync.

Answered from the vendors’ own pages

Asyncapi: What is AsyncAPI used for?

AsyncAPI is an open-source specification for defining and documenting asynchronous APIs, message-driven systems, and event-driven architectures. It serves the same purpose for async APIs as OpenAPI does for REST APIs, providing standardized documentation, code generation, and tooling.

Source
Windmill: What does Windmill cost?

Windmill's Free and Open-source edition is $0/month for self-hosted use with unlimited executions, while Enterprise starts at $120/month with unlimited workspaces and uncapped SSO seats, priced further by developer/operator seats and compute units.

Source
Asyncapi: Is AsyncAPI free to use?

Yes, AsyncAPI is completely free and open-source. It is hosted by the Linux Foundation and supported by community contributions and sponsorships from companies like Postman, IBM, IQVIA Technology, and Solace.

Source
Windmill: Is there a free plan and what are its limits?

The free self-hosted plan supports unlimited executions but caps SSO at 10 users, workspaces at 3, groups/permissions at 4, and email triggers at 100 per day.

Source
Asyncapi: What protocols and technologies does AsyncAPI support?

AsyncAPI supports multiple protocols and technologies including Kafka, RabbitMQ, MQTT, Socket.IO, AWS EventBridge, and others. It provides language support for JavaScript/TypeScript, Python, Java, Go, C#/.NET, Kotlin, and PHP.

Source
Windmill: How is usage metered on Windmill Enterprise?

Enterprise usage is metered through seats (developer seats at $20/month, operator seats at $10/month) and compute units, e.g. $100/month for 2 standard-worker compute units.

Source
Asyncapi: Does AsyncAPI have IDE support?

Yes, AsyncAPI has IDE extensions available for VSCode and IntelliJ, along with CLI utilities and GitHub Actions integration for developers.

Source
Windmill: What happens to a self-hosted Windmill deployment if the company shuts down?

The pricing page addresses this directly as an FAQ topic, noting that self-hosted applications built on the open-source edition can continue running independently of Windmill the company.

Source
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