10 Best API Testing Tools

An API testing tool helps you send a request to a service and inspect what comes back, without building a full application first. This roundup is for developers, students, and QA teams who need to check endpoints, save useful requests, or repeat tests as a project changes.

Some tools are visual desktop apps, others fit naturally in a terminal or in automated test suites. Try your actual authentication and team workflow before standardising; a tool that feels easy for one person may not suit shared or continuous testing.

Quick picks

• Best overall: Postman — broad features for individual requests and team collections.
• Best for open workflows: Bruno — collections stored as files with a Git-friendly approach.
• Best in a browser: Hoppscotch — quick requests without a large desktop setup.
• Best for automation: Karate — API tests written in a readable, code-oriented format.

How we picked

We considered how quickly each option helps a person make a request, inspect a response, and reuse a test. No single client replaces careful test design or secure handling of credentials.

• Request basics: methods, headers, query parameters, and response inspection.
• Repeatability: ability to save, organise, or automate checks.
• Team fit: sharing and collaboration options where relevant.
• Security: sensible handling of secrets and local project data.
• Accessibility: a reasonable learning curve for the intended user.

Request-building apps

1. Postman

Postman is a widely used API platform for sending requests, organising collections, and documenting workflows. Its environment variables and team features help move a set of requests from personal exploration toward shared work. The feature range can feel heavy when all you need is a single GET request, and teams should pay attention to plan limits and where secrets are stored. A free plan with paid upgrades is available.

Best for: teams who want one established workspace for requests, collections, and collaboration.

2. Insomnia

Kong Insomnia provides a desktop client for working with API requests and related specifications. Its request organisation and support for common API styles make it useful for developers switching between services during a day. Some collaboration and advanced workflows depend on account or plan choices, so compare the current offering with a local-only workflow. A free plan with paid options is available.

Best for: developers who prefer a focused desktop client for day-to-day API exploration.

3. Hoppscotch

Hoppscotch is a web-based API client for making requests and inspecting responses in a browser. Its fast, lightweight feel is convenient when checking an endpoint on a borrowed machine or starting a quick experiment. Browser permissions and network rules can affect requests, and sensitive credentials deserve extra care in any hosted interface. A free option is available, with additional offerings for teams.

Best for: learners and developers who want to try a request without installing a full client.

4. Bruno

Bruno is an open-source API client that stores collections as files in a project folder. That Git-friendly design lets developers review changes alongside application code rather than keeping all requests in a separate cloud workspace. Teams must agree on collection conventions, and some collaboration features differ from hosted-first tools. The core client is free and open source, with paid options available.

Best for: developers who want API collections versioned in the same repository as their code.

5. HTTPie

HTTPie offers a command-line HTTP client and a graphical application for exploring requests. The readable command syntax is a strong fit for people who want to run an API check in a terminal or script, while its interface can help newcomers inspect responses. Command-line use takes practice, and the desktop product's current capabilities and plan terms should be checked separately. A free tier with paid options is available.

Best for: terminal users who value readable commands and repeatable request snippets.

6. RapidAPI Client

RapidAPI includes an API client experience for building and testing requests, alongside its API discovery marketplace. The connection between browsing services and trying calls can be convenient when evaluating a third-party provider. Its marketplace is not a neutral guarantee of every API's reliability or terms, and users should check the source provider directly before depending on an endpoint. Free access and paid offerings vary by service and product.

Best for: developers exploring third-party APIs who want discovery and request testing in one ecosystem.

Automation and deeper testing

7. ReadyAPI

ReadyAPI is SmartBear's commercial testing suite for API workflows, including functional and load-oriented testing capabilities. It can suit established QA teams that need more than manually sending requests and want organised testing around services. The suite is more involved than a lightweight client, and its commercial plans may be excessive for a student's simple project. Paid product options are available; check current trial and licensing terms.

Best for: QA groups testing business APIs through a more structured desktop suite.

8. Katalon

Katalon provides a broader test automation platform that includes API testing alongside web and mobile testing workflows. Teams already using its test environment may benefit from keeping API checks near their other automated tests. It is a larger platform to learn than a stand-alone request tool, and features depend on product and plan. Free and paid offerings are available.

Best for: teams that want API checks connected to wider web or mobile test automation.

9. SoapUI

SoapUI is a long-running tool for testing web services, particularly useful for SOAP as well as REST scenarios. Its specialised capabilities help when maintaining older enterprise integrations that a simpler modern client may not cover comfortably. The interface and terminology can feel dated to newcomers, and users should distinguish the open-source edition from commercial ReadyAPI products. SoapUI is available as open-source software, with paid related products.

Best for: developers and testers maintaining SOAP services or mixed legacy integrations.

10. Karate

Karate is an open-source framework for API tests, with a readable syntax for describing requests and expected results. It is designed for repeatable automated checks, making it a stronger fit for build pipelines than one-off manual exploration. Framework-based testing requires project setup and some comfort with test concepts, so it may be too much for a quick endpoint check. Karate is open source.

Best for: developers who want readable API tests that can run repeatedly in a build workflow.

How to choose the right one

For a one-time investigation, a lightweight client is often enough; for a team, consider how collections are shared and whether changes belong in version control. If tests must run on every code change, choose an automation framework and check how it handles environment-specific secrets. Keep credentials out of screenshots, public repositories, and browser code. Inspect response status, headers, and body rather than deciding success from a green indicator alone. Stockio's JSON formatter can make response bodies easier to read, and the API latency tester helps compare endpoint timing. See also our development resources and public API ideas.

Key takeaways

• Use a client for exploration and a test suite for repeatable checks.
• Choose file-based collections if reviewing API changes in Git matters to your team.
• Check how secrets are stored before sharing a workspace or running tests in CI.
• SoapUI and ReadyAPI are relevant for SOAP and more structured enterprise testing.
• Start with the smallest tool that comfortably covers your real testing workflow.