A free API client sounds like a cut-down trial of something bigger, and for the eight here that isn't the case. Five are open source and three name a free plan or free tier on their own sites, so you can send requests, inspect responses and test APIs without buying a seat.
Developers and QA engineers need a client they can open in seconds, point at an endpoint and trust. The eight below cover local-first clients, a browser client, an editor extension, a terminal tool and a test automation suite, and they differ more in where your requests are stored than in what they can send.
The short answer for most developers
If you want your collections on your own machine and in version control, begin with the open-source, local-first clients. If your team already shares collections in a hosted platform, a free plan on that platform may be all a small team needs. If you live in your code editor, an extension saves a context switch, and if you script everything, a terminal client fits the way you already work.
None of that is a ranking. It's a sorting rule, and it'll get you to a shortlist of two faster than reading feature pages. The rest of this page explains the split that matters most and gives you a short trial to settle it.
Open source or a free plan, and why it matters
Here's what's easy to miss: free means two different things in this category. Bruno describes itself as open-source and local, built for developers. Yaak's source code is on GitHub under the MIT licence. HTTPie calls itself an open-source API testing client, Hoppscotch an open-source API development ecosystem, and SoapUI offers an open-source edition. Insomnia sits in both camps, with an open-source core and a free tier.
Postman and Thunder Client name a Free plan on their plans pages instead. A free plan is a product decision the vendor can revisit; an open-source licence lets you keep running the code you have. Neither is a problem in itself, but if your API collections are something you'd hate to lose access to, that difference is worth more than any single feature. One well-known testing tool isn't here because its page offers only a free trial.
Where each kind of client runs
The table's middle column does the sorting, but here's what each group means day to day.
Local-first and Git-based clients
Two of the open-source clients keep requests on your machine and store them in a form Git can version, so collections travel with your code and get reviewed like code. That suits teams who already do everything through pull requests.
API platforms and development clients
The broader platforms cover building and testing APIs across several protocols, and one lists HTTP, REST, GraphQL, gRPC, SOAP and WebSockets. They suit teams that design, test and share API work in one place.
Browser, editor and terminal
A browser client needs nothing installed. An editor extension sits inside VS Code and JetBrains, so you test an endpoint next to the code that serves it. A terminal client fits scripts, quick checks and anyone who'd rather type than click.
Automated test suites
One tool here is built around automated testing of SOAP and REST APIs rather than sending one-off requests. If you're writing regression suites for a QA team, that's the group to look at.
All eight, at a glance and A to Z
Alphabetical and in no particular order. Each line comes from what the maker says about its own tool.
| Tool | What kind of client | Who it suits |
|---|---|---|
| Bruno | Git-native API client | Teams keeping collections as code in Git |
| Hoppscotch | Browser API client | Developers who want to build requests fast in a browser |
| HTTPie | Terminal API client | Developers who test APIs from the command line |
| Insomnia | API client and design | Teams working across REST, GraphQL, gRPC and more |
| Postman | API platform | Individuals and teams building and testing APIs |
| SoapUI | API test automation | QA engineers automating SOAP and REST tests |
| Thunder Client | Editor-based API client | Developers testing REST and GraphQL inside their editor |
| Yaak | Local-first API client | Developers who want requests stored on their own machine |
Bruno
Best for: A Git-native client for REST, GraphQL, gRPC and WebSocket that stores collections as code; the vendor calls it local and open source.
Hoppscotch
Best for: An open-source API development ecosystem for building and sending requests; the vendor says it helps you create requests faster.
HTTPie
Best for: Testing APIs from the terminal with an open-source client that the vendor calls the original.
Insomnia
Best for: The vendor describes an open-source API development platform covering HTTP, REST, GraphQL, gRPC, SOAP and WebSockets in one client.
Postman
Best for: Building and testing APIs on a platform with a Free plan aimed at individuals; the vendor's own line is API engineering for your agents.
SoapUI
Best for: Automated testing of SOAP and REST APIs through an open-source edition, for building repeatable test suites.
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Thunder Client
Best for: Runs inside VS Code and JetBrains, handles GraphQL too and shares requests through Git; the vendor's claim is a fast, lightweight REST API client.
Yaak
Best for: Developers who keep API work beside their code: a local-first client whose vendor claim is your requests on your machine, versioned with Git.
A twenty-minute trial with your own API
Take two clients from different groups and put the same small job through both.
- Pick one real endpoint you work on, plus one that needs authentication.
- Send a request, inspect the response and save it into a collection or file.
- Add an environment variable for the base URL and switch between local and staging.
- Commit or share the collection the way your team would, then open it on a colleague's machine.
- Write one simple test that fails when the status code or a field changes.
Whichever client got you through step four with the least friction is the one to keep. Sharing is where most teams feel the difference.
What to check before a whole team switches
- Where collections are stored: on your machine, in Git or in the vendor's cloud.
- Whether the free route covers everyone who'll use it.
- Which protocols you need beyond REST, such as GraphQL, gRPC, SOAP or WebSockets.
- Whether you can import the collections you already have.
- How secrets and tokens are kept out of shared files.
Free plans and their limits change, so read each vendor's own page on the day you decide, not the week before.
For a solo developer or a small QA team
My advice is simple. A solo developer who already lives in Git should try the two local-first clients side by side and keep whichever feels faster. A small QA team writing repeatable suites should look hard at the test automation tool's open-source edition. A team that already shares a hosted workspace can stay on a free plan until it outgrows it, and there's no shame in that.
For the wider field, including tools without a free route, my guide to API testing tools covers it, along with these alternatives to the best-known API platform.
Do you make API testing or API client software? Tool makers can ask to be considered for a featured place on this list.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
What's the difference between open source and a free plan here?
An open-source client's code is published under a licence, so you can keep running it. A free plan is a tier the vendor offers and can change, so check each vendor's own page, because limits change.
Can I test GraphQL and gRPC with a free client?
Several clients in this list name GraphQL, and two name gRPC on their own pages. Check the protocol list on the vendor's site before you commit.
Is there a free API client that works inside my code editor?
Yes. One client here runs inside VS Code and JetBrains and names a free plan.
Can I keep API collections in Git?
Yes. Two clients here describe storing requests as files versioned with Git, and an editor extension shares requests through Git too.
Do I need a separate tool for automated API tests?
Not always, but one tool here is built around automated SOAP and REST testing, which helps if you're building suites for a QA team.
Will these tools stay free?
Open-source licences and free plans are stated on each vendor's page, but plan limits change. Check the vendor's own page before you rely on one for a team.
