Free and open first

Best API Development Tools in 2026

32 apps
Research read 28 Sept 2026
How the order is worked out

1

Bruno

Free plan Open source APIExtensionLinux+3

Bruno pairs API testing and automation with Git-friendly plain-text collections and companion tools.

9.2 Free plan · paid from $6/user/mo (annual) · 14-day trial Visit site
2

HTTPie

Free plan Open source LinuxMacWeb+1

HTTPie offers command-line API testing alongside a graphical app for desktop and web. The CLI plan is open-source, while the Desktop and Web plan is in public beta; both are listed as free.

9.2 Free plan Visit site
3

Scalar

Free plan Open source APILinuxMac+3

Scalar brings several API documentation and management tools together, with hosted and self-hosted options.

8.8 Free plan · paid from $150/mo Visit site
4

SoapUI

Free plan Open source APILinuxMac+2

SoapUI Open Source offers API testing, mocking, and command-line automation across major listed protocols.

8.8 Free plan Visit site
5

Apidog

Free plan APIExtensionLinux+4

Apidog combines API design, testing, mocking, and documentation with specification-driven workflows and deployment choices. Check the plan details and database limits against your team's requirements.

7.7 Free plan · paid from $9/user/mo (annual) · 14-day trial Visit site
6

Beeceptor

Free plan APILinuxMac+3

Beeceptor combines configurable mocks with proxying, traffic recording, and failure simulation across a wide range of API protocols.

7.6 Free plan · paid from $10/mo · 10-day trial Visit site
7

HTTP Toolkit

Free plan AndroidiPhoneLinux+3

HTTP Toolkit offers a free starting point for traffic inspection and manual breakpoints, with automation and reusable rules in Professional.

7.5 Free plan Visit site
8

Hurl

Free plan LinuxMacSelf-hosted+1

Hurl combines request workflows, response assertions, and CI reporting in a free command-line tool. Check the listed Linux and Windows requirements before choosing an installation option.

7.5 Free plan Visit site
9

Insomnia

Free plan LinuxMacSelf-hosted+1

Insomnia covers API design and client workflows alongside mocking, CI/CD execution, and team collaboration.

7.5 Free plan · paid from $12/user/mo · 14-day trial Visit site
10

Assertible

Free plan APIWeb

Choose Assertible if you need HTTP service checks, deployment smoke tests, or API test synchronization with common specification formats and Postman collections.

7.4 Free plan · paid from $25/mo Visit site
11

Mockoon

Free plan APILinuxMac+3

Mockoon covers local mock creation as well as automated, serverless, and private deployment workflows.

7.4 Free plan · paid from $100/mo (annual) Visit site
12

OpenAPI Generator

Free plan LinuxMacSelf-hosted+2

OpenAPI Generator covers client, server-stub, and documentation generation, with options to customize output and integrate with common build workflows.

7.4 Free plan Visit site
13

Pact

Free plan APILinuxMac+2

Pact focuses on contract-based integration checks, with tools for HTTP, messaging and deployment compatibility workflows.

7.4 Free plan Visit site
14

Postman
by Postman
Free plan ExtensionLinuxMac+2

Postman combines API creation, testing, documentation, and monitoring in one platform, with a free plan and paid options. Check plan availability and the annual billing terms before choosing a tier.

7.4 Free plan · paid from $9/mo (annual) Visit site
15

Kreya
by Kreya
Free plan LinuxMacWindows

Kreya combines broad protocol support with scripted and snapshot testing, imports, and CI/CD use.

7.3 Free plan · paid from $5/user/mo · 10-day trial Visit site
16

Schemathesis

Free plan LinuxMacSelf-hosted+1

Schemathesis provides schema-based API testing with adaptive and stateful workflows, authentication options, and CI/CD integrations.

7.2 Free plan Visit site
17

Redocly
by Redocly
Free plan APIExtensionWeb

Redocly brings API references, collaboration, governance, and monitoring into one product set, with an open-source CLI and VS Code extension.

7.1 From $10/user/mo · 30-day trial Visit site
18

Speakeasy

Free plan APILinuxMac+2

Speakeasy brings MCP governance, workflow assistants, and API tooling into one platform. Teams evaluating the Enterprise plan will need to request pricing.

7.1 Free plan · pricing on request · 14-day trial Visit site
19

Stainless

Free plan LinuxMacWeb

Stainless brings SDK generation, API documentation, and code-mode MCP servers together around OpenAPI.

7.0 Free plan · 30-day trial Visit site
20

Testfully
by Testfully
Free plan ExtensionLinuxMac+2

Testfully combines API testing, monitoring, and team collaboration across cloud and offline workspaces.

7.0 Free plan · paid from $14/user/mo (annual) · 14-day trial Visit site
21

Thunder Client
by Thunder Client
Free plan ExtensionLinuxMac+1

Choose Thunder Client if you want an API client inside your IDE, with local data storage and graphical response validation.

7.0 Free plan · paid from $3/user/mo (annual) · 14-day trial Visit site
22

ReadMe
by ReadMe
Free plan Web

6.9 Free plan · paid from $250/mo (annual) · 14-day trial Visit site
23

WireMock

Free plan APILinuxSelf-hosted+1

WireMock offers request matching, response simulation, and replay for testing against simulated dependencies.

6.9 Free plan Visit site
24

Stoplight Elements

Free plan Self-hostedWeb

Stoplight Elements covers core interactive API documentation needs with OpenAPI support, code examples, and an embedded console.

6.8 Free plan Visit site
25

Yaak

Free plan LinuxMacWindows

Yaak brings API requests and Git-oriented organization together in a desktop client with local data storage.

6.8 Free plan · paid from $79/user/yr · 30-day trial Visit site

#1Places #1, #2, #3, #4, #5 on this list can be bought by the makers of the software on it. See the price

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