Workflow Automation

Atmo

Server-side API mocking for seamless development and testing.

Status
UnmaintainedNo commits in 3155 days.
Last checked
Checked · Oct 13, 2026
License
Open source
Pricing
Free tier · from $0
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What it is

Atmo is an open-source tool that allows developers to create server-side mocks of APIs, enabling them to test their applications without relying on external services. This makes it easier to develop and test features locally before deploying them.

Atmo stands out by offering an open-source solution that can be easily integrated into projects as a library, making it ideal for developers who need server-side API mocking without the overhead of setting up cloud-based services.

When it fits — and when it doesn’t

A good fit for

  • Teams working with JavaScript or TypeScript who need a reliable way to mock server-side APIs during development and testing phases.

  • Developers looking for an open-source solution that can be easily integrated into their existing projects as a library.

Look elsewhere if

  • Projects requiring cloud-based API mocking services, as Atmo is designed for local use.

  • Teams working with languages other than JavaScript or TypeScript, as support is limited to these languages.

Known weaknesses

Each one links to the public issue, changelog or docs page it came from, where we have one.

  1. 01

    Limited integrations with other testing frameworks

    Official support is only for Jest and Mocha, lacking popular alternatives like Cypress or Playwright

  2. 02

    Performance issues under heavy load

    Mocking complex API interactions can lead to significant slowdowns in test execution times

What it does well

  • Server-side API mocking for seamless development and testing.

  • Supports both JavaScript and TypeScript.

  • Easy to integrate into existing projects as a library.

Pricing

Free tier
YesOpen source — free to use
Paid from
$0
Model
Flat rate
Enterprise plan
No

Pricing last confirmed Sep 27, 2026.

Performance benchmarks

How Fast Is It?

Set up Atmo

Setup steps, common gotchas and what to check after 30 days.

Open the setup guide →
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