best api testing tools for rest apis in 2025

rest apis power most of the web today. whether you're shipping a microservice, a mobile backend, or a third-party integration, testing those endpoints is non-negotiable. the tooling has matured fast: we've gone from pasting curl commands into a terminal to full lifecycle platforms that handle design, mocking, automation, and monitoring in one place.1

the hard part is picking the right one. do you need a rich gui for exploratory testing? a code-first library that lives in your ci/cd pipeline? something that works for both api and ui tests? here's our breakdown of the five best api testing tools for rest apis in 2025, categorized by how teams actually use them.

the picks at a glance

1. postman — best for enterprise api lifecycle management

postman is the most widely adopted api client in the world, and for good reason. it's evolved from a simple request builder into a full api platform covering design, documentation, mock servers, automated testing, and monitoring.1

what makes postman stand out is its collaboration layer. teams can share collections, environments, and test results in real time. the scripting engine (based on node.js) lets you write pre-request and post-response tests, chain requests, and integrate with ci/cd pipelines. for enterprise teams that need governance, role-based access, and audit trails, postman is the default choice.2

the trade-off? it's heavy. the desktop app can feel bloated, and the cloud-first storage model means your collections live on postman's servers unless you export them manually. the free tier is generous but the features you actually want (team collaboration, mock servers, monitoring) require a paid plan.

verdict: if you're on a team that needs a shared api workspace with full lifecycle tooling, postman is still the standard.

2. insomnia — best for developers who want a clean ux and graphql support

insomnia started as a leaner alternative to postman and has carved out a loyal following among developers who value a clean, fast interface.1 its graphql support is best-in-class — you can write queries, mutations, and subscriptions with autocomplete and a visual schema browser.

insomnia's environment management is straightforward, and the plugin ecosystem lets you extend functionality without the bloat. it supports local storage by default, with optional cloud sync via insomnia cloud or self-hosted options.

the catch: the collaboration features aren't as mature as postman's. if you need fine-grained team permissions or enterprise governance, you'll hit limits. but for individual developers and small teams who want a polished, distraction-free client, insomnia is a strong pick.

verdict: the best choice for graphql-heavy projects and developers who prioritize ux over enterprise features.

3. rest assured — best for java developers writing ci/cd tests

rest assured is a java dsl for testing rest apis that integrates directly into your test suite. you write fluent, readable assertions like given().when().get(\"/api/users\").then().statusCode(200) — no gui, no external client, just code that runs in your build pipeline.2

because it's a java library, it fits naturally into junit or testng workflows, maven/gradle builds, and ci/cd systems like jenkins or github actions. you get full control over requests, validation, serialization, and authentication — all in your existing test framework.

the downside: it's java-only, and it's purely code-based. if your team prefers visual testing or includes non-developers, rest assured isn't the right fit. but for java shops that want automated, repeatable api tests as part of every build, it's the gold standard.

verdict: essential for java teams that need programmatic api testing baked into ci/cd.

4. karate — best for bdd teams and test unification

karate takes a different approach: it combines api testing, mocks, performance testing, and even ui testing into a single framework, using a simplified gherkin-like syntax that doesn't require cucumber or step definitions.2

the syntax is remarkably readable — you write scenarios in plain text files that look almost like documentation, then run them as tests. karate handles json/xml parsing, assertion, and even data-driven testing out of the box. it also includes a built-in mock server and the ability to run performance tests with gatling.

the trade-off: it's another framework to learn, and while the syntax is simpler than cucumber, it's still a new paradigm for teams used to traditional testing. but for teams already practicing bdd or looking to unify api, web, and performance testing in one tool, karate is uniquely powerful.

verdict: a standout choice for bdd teams and anyone wanting a single framework for api + ui + perf testing.

5. katalon studio — best for low-code unified testing

katalon studio positions itself as a unified test automation platform covering api, web, mobile, and desktop testing from a single interface.2 its dual-mode approach — a visual gui for test creation alongside a full script editor — makes it accessible to both manual testers and automation engineers.

for api testing specifically, katalon supports rest, soap, and graphql with built-in assertions, data-driven testing, and ci/cd integration. the object spy and recording features reduce the learning curve for teams transitioning from manual to automated testing.

the catch: katalon is a heavier tool, and the free tier has limitations on execution and reporting. it's also not open-source, which may be a concern for some teams. but for organizations that want a single tool for both api and ui testing with a low-code entry point, it's a solid option.

verdict: best for teams that need a low-code, all-in-one testing platform spanning api and ui.

how to choose

here's a quick decision framework:

• you need enterprise collaboration, mock servers, and monitoring → postman
• you work heavily with graphql and want a clean desktop client → insomnia
• you're a java shop writing ci/cd tests → rest assured
• you practice bdd or want one framework for api + ui + perf → karate
• you want a low-code tool that handles api and ui testing → katalon studio

the good news: all five tools have free tiers or are open-source, so you can try them without commitment. start with the one that matches your team's workflow, not the one with the most features.

disclosure: askbuy earns affiliate commissions when you purchase through some of the links on this page. this does not influence our recommendations — we only recommend tools we've evaluated and believe provide genuine value.