Designing an API and publishing its reference look like one job from the outside, but the tools that replace a design platform usually split them apart. Docs platforms turn an OpenAPI file into pages, API clients send and check requests, and a governance suite keeps specs in line. Work out which of those you leaned on, then shortlist from that group.
Stoplight describes itself as an OpenAPI design and documentation platform, and it also ships open-source projects called Spectral, Prism and Elements. That spread is why leaving it can feel like a bigger move than it needs to be. Most teams were relying on one or two parts of it, not the whole thing, so the ten tools below, in no particular order, are sorted by the work they do rather than by any idea of which is better.
Splitting an API platform into the work it did for you
A design platform tends to sit across three different moments in an API's life. Someone writes or edits the spec. Someone publishes docs from it so other developers can find their way around. Someone sends requests to the endpoints it describes and checks what comes back. Those are three different people on many teams, working in three different places: a pull request, a public docs site and a laptop or pipeline.
When one product held all three together, nobody had to think about where each job lived. Once you move, you do. So before you look at a single tool, go back over the past few weeks and ask which part of the old platform people opened most. If it was the published reference, you're shopping for a docs platform. If people mostly fired requests and read responses, you need an API client. If the thing you'd miss is design rules applied across many specs, you're after governance tooling.
Plenty of teams will land on two of those, and that's fine. What tends to go badly is picking one big product and hoping it covers the job you didn't check.
How these ten divide up by job
Five tools here are docs platforms, and they differ mainly in what they treat as the source of truth. Redocly and Bump.sh both build from your API description and add things around it, such as linting, mocks or a changelog. Scalar starts from one OpenAPI document and generates more than pages from it. Mintlify and ReadMe lean towards a fuller developer hub, where guides and written explanations sit alongside the reference.
Four are API clients, and the split there is about where your work is stored and who can see it. Postman covers discovery, monitoring and mocks as well as requests. Insomnia puts collaboration and Git sync in front. Hoppscotch and Bruno are both open source, with one spread across web, desktop and CLI and the other keeping collections as plain files in your repository.
The last one is a design and governance suite, which is a different kind of purchase again: less about a single developer's day and more about keeping many APIs consistent across a company.
Who looks after the old platform now
The site of the platform you're leaving now says its support runs through the SmartBear Community. SmartBear also runs Swagger, the design and governance suite on this page, so a move there keeps you inside the same company rather than taking you somewhere new.
That isn't a reason to rule it out. If your team already knows the company and its way of working, staying close can be the calm choice. It's a reason to be clear about what you're trying to change. If the goal is a different support route, a different roadmap or less dependence on one vendor, a suite from the same owner may not give you that, and you should ask the questions directly before you plan a migration around it.
Whichever way you lean, test the dull things first: does your existing spec import cleanly, do your design rules survive the move, and can the people who answer your support questions see your setup.
Ten replacements listed alphabetically
In no particular order beyond the alphabet. Each line is a short description drawn from what the maker says about its own product, with the maker's own claims marked as theirs.
Bruno
Best for: Developers who want collections saved as plain-text files in their own repo; the vendor's line is that it's an API client, not a platform.
Bump.sh
Best for: Publishing doc portals from OpenAPI or AsyncAPI files; vendor claim: it rebuilds the docs and the MCP server on every release.
Hoppscotch
Best for: Sending and checking requests from an open-source client on web, desktop or CLI, which the vendor says runs offline, on-prem or in the cloud.
Insomnia
Best for: Teams designing, debugging and mocking APIs together with Git sync; vendor claim: no login is ever required for its Scratch Pad.
Mintlify
Best for: Documentation meant to stay readable for people and AI agents alike; the vendor describes it as self-updating documentation.
Postman
Best for: Discovering, testing, mocking and monitoring APIs, now with a CLI aimed at AI agents, which the vendor says uses fewer tokens.
ReadMe
Best for: A developer hub holding guides, recipes and API reference, with AI translations and an MCP server listed by the vendor.
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Redocly
Best for: Reference pages, a mock server and linting from one docs platform with an open-source CLI; vendor claim: it scores your API description for agent-readiness.
Scalar
Best for: Generating docs, SDKs and hosted MCP servers from a single OpenAPI document, which the vendor says stays hosted, observed and in sync.
Swagger
Best for: Design, testing and governance tooling; vendor claim: it sets the standard for API design, testing and governance in the age of AI.
All ten side by side
The same ten, with the kind of tool each one is and the work it's aimed at.
| Tool | Kind of tool | Aimed at |
|---|---|---|
| Bruno | Git-native API client | Teams keeping API collections in Git |
| Bump.sh | API doc platform | Docs portals that change with each release |
| Hoppscotch | Open-source API client | Open source requests on web, desktop or CLI |
| Insomnia | API client and design | Collaborative design, debugging and mocking |
| Mintlify | Docs platform | Docs read by people and AI agents |
| Postman | API platform and client | Testing, mocking and monitoring in one place |
| ReadMe | API documentation hub | Developer hubs with guides and reference |
| Redocly | API docs and linting | Reference docs plus linting and mocks |
| Scalar | API docs and MCP hosting | Docs, SDKs and MCP from one spec |
| Swagger | API design and governance suite | Design rules and governance across APIs |
Running one real endpoint through two tools
Don't trial these with a sample pet store. Take one endpoint your team supports today, ideally one with an awkward request body or an authentication step, and the OpenAPI file it lives in. Pick two tools from the group that matches the job you're replacing, and give each the same afternoon.
For a docs platform, import the spec, publish a preview and read the result as an outside developer would. Look at how errors, examples and auth are shown, and how much you had to fix by hand. For an API client, send the request, save it, share it with a colleague and see where the saved file ends up. That last part decides whether your collections live in a vendor's account or in your own repository, which matters more a year from now than any feature does.
Write down what broke and what you had to work around. The tool with the shorter list usually tells you what you need to know.
Where an API team should begin the move
Start with the job you can't do without for a week, which for most teams is the published reference that outside developers depend on. Move that first, keep the old setup running beside it, and only switch the testing and governance side once the docs are stable. If your team is weighing the docs side more broadly, my list of API documentation tools goes wider on that one job, and there's a separate look at options for leaving the SmartBear-run design suite too.
Do you make API design, documentation or testing tools? 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
Can I keep using my existing OpenAPI files?
That's the first thing to check. The docs platforms here describe themselves as working from OpenAPI documents, so import a real spec of yours and look at what renders before you plan anything else.
Do I need both a docs platform and an API client?
Often, yes, because they do different jobs. Docs are for the people using your API, while a client is for the people building and testing it. Many teams end up with one of each.
Are there open-source options in this list?
Two of the API clients describe themselves as open source, and one docs platform mentions an open-source CLI. Check each project's own site for what that covers.
Is moving to a suite from the same company a real change?
It depends on what you want to change. If you're after a different owner or support route, it won't give you that. If you're happy with the company, it can be the least disruptive move.
What does MCP mean on these docs tools?
Several of the docs platforms say they generate or host MCP servers, which let AI agents read your API. If agents are part of how your API gets used, test that output alongside the human-facing pages.
How long should a trial take?
An afternoon per pair of tools is enough to find the deal-breakers, as long as you use a real endpoint and your own spec rather than a demo.
