Free API Testing Tools and API Clients
Which API clients and API testing tools a startup team can use for free today, how far the free plan goes, what team collaboration it allows, whether a card is needed and what the first paid plan costs, read from each tool's own page.
Free allowances read on each provider's own pages, all checked on or after . API tools change their free plans from time to time: confirm the terms on the tool's page before your team moves its collections there.
API clients and testing tools a startup can use for free today include Postman (API client and core tools, free), Mockoon (Free and open source (MIT)), Insomnia (Free: unlimited Cloud and local projects), Beeceptor (Forever-free mock API plan), and Hoppscotch (Free and open source (MIT license)). Each of the 12 free plans below links to the tool's page that states it, with its main limit, what team collaboration it allows, whether a card is needed and what the first paid plan costs.
Every team that builds or calls an API needs a client to send requests and, soon, mocks and checks to keep it working. The leading API clients have a free plan, and several are open source and free outright.
The headline rarely tells you how far it goes. A free plan can stop at one user, cap mock server requests or requests per collection, or be free only for personal use. Each tool below shows what is free, its main limit, what team collaboration it allows, whether a card is needed and what the first paid plan costs, quoted from the tool's own page with the date we read it.
Which tools we picked and the order they appear in are our editorial choices; the terms are the providers'. Some of these providers pay us a referral commission when someone signs up through our link: those links are labeled, and they play no part in which tools are listed or where.
API clients with a free plan
Send and organize API requests, with a free plan or free and open source.
- 1
Postman
The best-known API client, for one person
Postman's Free plan is an API client for one user. Solo, the first paid plan, is $9 a month billed annually.
- Main limit
- 1 user only (source: postman.com)
- First paid plan
- Solo: $9 a month, billed annually (source: postman.com)
- 2
Insomnia
A free API client with Git sync for a small team
Insomnia's Essentials plan is free, with unlimited Cloud and local projects, Git Sync for up to 3 users and 1,000 mock server requests a month. Pro is $12 per user a month.
- First paid plan
- Pro: $12 per user a month (source: insomnia.rest)
- 3
Hoppscotch
An open-source API client you can self-host
Hoppscotch is free and open source under the MIT license, and you host it yourself. Its Enterprise Edition is $19 per user a month, billed monthly.
Start free at HoppscotchTerms read on docs.hoppscotch.io on Hoppscotch: the free allowance and how to start - 4
Bruno
A free, open-source Postman alternative
Bruno's Open Source plan is free, with 2 workspaces. Pro is $6 per user a month, billed annually.
- What's free
- Free and open source (source: usebruno.com)
- Main limit
- 2 workspaces (source: usebruno.com)
- 5
Apidog
Small teams of up to 4 people, API design and tests
Apidog's Free plan is for teams of up to four members, with API recovery and change history kept for 7 days and no credit card. Paid plans start at $9 per user a month.
- Payment card
- No card needed (source: apidog.com)
- First paid plan
- Paid plans from $9 per user a month (source: apidog.com)
- 6
Thunder Client
A free API client inside VS Code
Thunder Client's Free plan needs no credit card and allows 50 requests per collection. Starter is $3 per user a month, billed annually.
- Payment card
- No card needed (source: thunderclient.com)
Start free at Thunder ClientTerms read on thunderclient.com on Thunder Client: the free allowance and how to start - 7
Yaak
Individuals using it for personal projects
Yaak is free for personal use, and a license is only required when you use it at work. The Individual license is $79 a year.
- What's free
- Free for personal use (source: yaak.app)
- First paid plan
- Individual: $79 a year (source: yaak.app)
API testing, mocking and monitoring with a free tier
Mock servers, contract tests and API checks, with a free tier to start.
- 1
Mockoon
Mocking REST APIs on your own machine
Mockoon is free and open source under the MIT license, and you do not need an account to use it. Team collaboration is in the separate Pro version.
- Main limit
- No account needed (source: mockoon.com)
- 2
Beeceptor
Quick mock endpoints with no sign-up
Beeceptor's forever-free plan includes dynamic and conditional mock responses, with 50 requests a day per endpoint and no credit card. Individual is $10 a month.
- Payment card
- No card needed (source: beeceptor.com)
- First paid plan
- Individual: $10 a month (source: beeceptor.com)
Start free at BeeceptorTerms read on beeceptor.com on Beeceptor: the free allowance and how to start - 3
Assertible
API tests and uptime checks for one person
Assertible's Personal plan is free, with 2 monitors and no time limit. The paid Standard plan is $25 a month, after a free month.
- First paid plan
- Standard: $25 a month (source: assertible.com)
Start free at AssertibleTerms read on assertible.com on Assertible: the free allowance and how to start - 4
Step CI
Developers who test APIs as code in YAML or JS
Step CI's open-source runner and CLI stay free and run on your own network and in CI/CD. A custom Support Plan adds support with an SLA.
- First paid plan
- Support Plan: custom pricing (source: stepci.com)
- 5
Katalon
Testers who want a free desktop test studio
Katalon Studio's Free plan lets you author and run tests locally. The Professional plan starts at $84 per seat a month.
- First paid plan
- Professional: from $84 a seat a month (source: katalon.com)
Also useful for founders
Referral links, picked for fit and ordered by fit (70%) and what a signup earns us (30%), at no cost to you. They never change this page's ranking.
ScraperAPIScraping API that handles proxies, browsers and CAPTCHAs for you1,000 API creditsReferral link
Parallel AIAutonomous AI agents for sales, marketing and support50 free credits, no cardReferral link
ColdIQOne API and MCP server for B2B sales data from 40+ providers300 free creditsReferral linkCompare the top options
How this comparison is built
The list covers API clients and API testing tools a founder can use for free today without applying to a program. The order and the "best for" notes are our editorial reading of each tool's terms. Every term comes from the tool's own pricing or help page on the date shown, never from a third-party list; follow each link for the full conditions. A cap on collaborators or collection runs can matter more than the headline, so the comparison quotes them wherever the tool states them. Some of these tools pay StartupPerks a referral commission, and their links are labeled as referral links; that decides neither whether nor where a tool appears, and no tool pays for a placement on this page.
Read the full methodologyCommon questions
What is the best free API testing tool?
It depends on the team. By the terms each tool states, Apidog is free for up to 4 members, Insomnia's free plan includes unlimited cloud and local projects with 1,000 mock server requests a month, Postman's free plan is for 1 user, and Bruno, Hoppscotch and Mockoon are free and open source.
Is Postman free?
Postman's free plan includes its API client and core tools for 1 user. Solo costs $9 a month, billed annually.
What is a free Postman alternative?
Bruno and Hoppscotch are free and open source, Insomnia's free plan includes unlimited projects, and Apidog is free for up to 4 members.
Is there a free mock API server?
Mockoon is free and open source with no account needed, and Beeceptor's forever-free plan allows 50 requests a day per endpoint.
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