API Advice

In Depth: Speakeasy vs Stainless

Nolan Sullivan

September 10, 2025 - 8 min read

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In this post, we’ll compare generated SDKs, as well as the underlying philosophies that guide the development of the two companies. And while we acknowledge that our views may be biased, we’ll show our work along with our conclusions so that readers can decide for themselves.

In short: How is Speakeasy different?

OpenAPI-native vs OpenAPI-compatible

Speakeasy is OpenAPI-native; Stainless is OpenAPI-compatible. Stainless is built on a custom DSL known as the Stainless config . This approach requires your team to manage an additional config file. Speakeasy has no intermediary DSL. Your OpenAPI spec is the only source of truth for SDK generation.

Being OpenAPI-native is beneficial for integration into an existing stack. Regardless of the API proxies, server-side code, or specific web framework that you’re using, you can plug in Speakeasy’s tools. Stainless is doubling down on a vertically integrated approach by building a backend TypeScript framework  which will become the foundation for their solution. Their product will work best when you buy the entire stack, Speakeasy will shine regardless of the other tools in your existing stack.

Type-safe vs type-faith

There’s more on this topic in the technical deep dive below. Speakeasy SDKs guarantee true end-to-end type safety with runtime validation using Zod schemas, meaning that types are generated to validate both request and response objects defined in your API. Stainless SDKs, on the other hand, are mainly type-hinted, not guarding the API from bad inputs.

Velocity and maturity

Stainless was founded in 2021  and has expanded its language support to seven languages. By comparison, Speakeasy launched in October 2022 and has released support for ten languages in less time. The Speakeasy platform is also broader, with support for additional generation features, like webhooks, React Hooks, and contract testing, not supported by Stainless.

Both companies are financially secure, having raised $25M+ in funding.

Platform

SDK generation

If there’s a language you require that we don’t support, add it to our roadmap .

SDK features

Breadth matters, but so does the depth of support for each language. The table below shows the current feature support for Speakeasy and Stainless’s SDK generation.

Pricing

In terms of pricing, both Speakeasy and Stainless offer free plans, as well as paid plans for startups and enterprises. The most significant pricing difference is in the enterprise plan. Existing customers indicate that Stainless’s enterprise pricing is ~20% higher than Speakeasy’s. Of course, this can vary, and we recommend reaching out to both companies for a quote.

Speakeasy vs Stainless: TypeScript SDK comparison

SDK structure

The Vercel SDK (generated by Speakeasy) maintains a clear separation of concerns with dedicated folders for models, operations, hooks, and comprehensive documentation. Each component and operation has its own file, making the codebase easy to navigate and understand.

The Cloudflare SDK (generated by Stainless) organizes code differently, with a flatter structure under resources and extensive runtime shims for cross-platform compatibility. While this approach supports multiple JavaScript runtimes, it results in more configuration files and less clear separation between different types of code.

Structure affects developer experience. SDK users form their first impressions from the high-level organization, and a well-structured SDK suggests quality and maintainability to developers evaluating whether to adopt it.

Dependencies and bundle size

One key difference between Speakeasy and Stainless approaches is their dependency philosophy, which directly impacts bundle size and security surface area.

While the Cloudflare SDK’s dependencies serve specific purposes (cross-platform compatibility, streaming support, etc.), all of that functionality can be achieved with minimal external dependencies as shown by the Speakeasy generated SDK.

Generated types and type safety

Both Speakeasy and Stainless generate TypeScript types, but they differ significantly in their approach to type safety. Speakeasy generates types with runtime validation using Zod, while Stainless relies primarily on compile-time TypeScript checking.

Let’s examine how each handles creating a deployment with project configuration:

The Vercel SDK generates Zod schemas that validate data both at compile time and runtime, catching type errors before they reach the server. The Cloudflare SDK provides excellent TypeScript types but relies on server-side validation to catch runtime errors.

This difference becomes critical when dealing with dynamic data or complex validation rules that can’t be fully expressed in TypeScript’s type system.

Runtime type checking

Speakeasy creates SDKs that are type-safe from development to production. As our CEO wrote, type safe is better than type faith.

The Vercel SDK uses Zod  to validate data sent to and received from the server. This provides safer runtime code execution and helps developers catch errors before making API calls.

Here’s what happens when invalid data is passed to each SDK:

The Vercel SDK catches type errors immediately with Zod validation, providing clear error messages before making HTTP requests. The Cloudflare SDK relies on server-side validation, meaning invalid data is sent over the network and errors are discovered later.

This difference is crucial when dealing with dynamic data, user input, or complex validation rules that can’t be fully expressed in TypeScript’s type system.

Authentication handling

Both SDKs handle authentication, but with different approaches and levels of built-in sophistication.

The Vercel SDK (generated by Speakeasy) uses bearer token authentication with simple configuration. Authentication is handled automatically for all requests, with no additional setup required.

The Cloudflare SDK (generated by Stainless) uses API token authentication and provides comprehensive error handling with specific error classes for different authentication scenarios, including AuthenticationError, PermissionDeniedError, and other HTTP status-specific errors.

When it comes to OAuth 2.0 support, Speakeasy-generated SDKs include built-in OAuth 2.0 client credentials handling with automatic token lifecycle management, retries, and error handling. This means the SDK automatically fetches, stores, and refreshes tokens as needed without requiring additional code.

Stainless-generated SDKs typically require manual OAuth implementation when OAuth is needed, meaning developers must write additional code to handle token acquisition, storage, refresh logic, and error recovery.

Webhooks support

Speakeasy-generated SDKs provide built-in support for webhook validation, payload parsing, and delivery with automatic signature verification using HMAC or other signing algorithms. The generated SDK includes strongly-typed webhook event handlers based on the OpenAPI specification.

The Vercel SDK includes webhook handling capabilities as part of its comprehensive feature set, allowing developers to validate and process webhook events with minimal setup.

Stainless-generated SDKs typically don’t provide out-of-the-box webhook functionality. The Cloudflare SDK focuses primarily on API calls rather than webhook handling, requiring developers to implement their own logic for verifying event signatures, defining event payload types, and managing webhook delivery mechanisms.

This difference means that APIs requiring webhook support benefit significantly from Speakeasy’s built-in webhook validation and type-safe event handling, while Stainless users must build these features manually.

You can read more about how Speakeasy handles webhooks in our webhooks release post.

React Hooks

React Hooks simplify state and data management in React apps, enabling developers to consume APIs more efficiently. Speakeasy generates built-in React Hooks using TanStack Query . These hooks provide features like intelligent caching, type safety, pagination, and integration with modern React patterns like SSR and Suspense. Stainless does not generate React Hooks.

For example, in this basic implementation, the useQuery hook fetches data from an API endpoint. The cache key ensures unique identification of the query. The status variable provides the current state of the query: loading, error, or success. Depending on the query status, the component renders loading, error, or the fetched data as a list.

For an in-depth look at how Speakeasy uses React Hooks, see our official release article.

Summary

We’ve all experienced bad SDKs that make integration with the API harder, not easier. Speakeasy is building a generator to make poorly written, poorly maintained SDKs a thing of the past. To do so, our team has put an extraordinary level of thought into getting the details of SDK generation right. We think that the effort has earned us the position to compare favorably with any other generator.

If you are interested in seeing how Speakeasy stacks up against some of the popular open-source SDK-generation tools, check out this post.