Postman vs Insomnia vs Thunder Client: Which API Client Should You Use in 2025?

Three tools dominate the conversation whenever developers argue about API clients. Postman has roughly 30 million registered users and a valuation north of $5 billion. Insomnia, acquired by Kong in 2019, has carved out a loyal following among developers who want something lighter. Thunder Client, a relative newcomer, crossed 5 million installs in the VS Code Marketplace by doing one thing well: keeping you inside your editor.

The catch is that all three changed significantly in the past two years. Postman pushed hard into API governance and AI-assisted tooling. Insomnia went through a controversial account requirement and a partial walk-back. Thunder Client added a paid tier. Picking the right one in 2025 means looking at where each tool is actually headed, not where it was in 2021.

The Short Answer

If you want a quick recommendation before the details:

  • Postman — best for teams that need collaboration, API documentation, mocking, and governance in one platform.
  • Insomnia — best for individual developers and small teams who want a fast, clean client with strong support for GraphQL, gRPC, and REST.
  • Thunder Client — best for developers who live in VS Code and want lightweight request testing without leaving the editor.

Now the reasoning.

Postman: The Platform Play

Postman stopped being “just an API client” years ago. It’s now a full API lifecycle platform, and that’s either its greatest strength or its biggest annoyance, depending on what you need.

What works well:

  • Collection runner and automation. Running a folder of requests with data files and assertions is genuinely useful for smoke tests and regression checks.
  • Mock servers and documentation. You can generate a public or private API docs page from a collection in minutes. For teams shipping APIs to external consumers, this saves real work.
  • Environment and variable management. Postman’s variable scoping (global, collection, environment, local) is more granular than what competitors offer.
  • Team collaboration. Shared workspaces, comment threads, and change history make it viable for teams of 10 or more.
  • The API Network. Public collections from companies like Stripe and Twilio are genuinely handy reference material.

Where it grates:

  • Resource usage. The desktop app is Electron-based and memory-hungry. On a machine already running Docker, a browser with 40 tabs, and an IDE, Postman can be the straw that breaks the RAM budget.
  • Account requirements and cloud sync. You can use Postman without signing in, but many features assume you’re logged in and syncing to the cloud. For developers in regulated industries, that’s a non-starter without the enterprise plan.
  • Pricing. The free tier is generous for individuals. Team plans start around $14 per user per month (billed annually), and enterprise pricing requires a sales conversation. Costs add up fast for larger teams.

Verdict: Postman is the right call when API work is a team activity and you need documentation, mocking, and governance. For a solo developer testing endpoints, it’s often more tool than necessary.

Insomnia: The Developer’s Client

Insomnia’s pitch has always been simplicity. Open it, create a request, send it, done. That focus still holds in 2025, though the tool has grown more capable.

What works well:

  • Clean, fast interface. Insomnia feels lighter than Postman, both visually and in terms of system resources. Startup is quick.
  • First-class GraphQL support. The GraphQL query editor with schema introspection and autocomplete is arguably better than Postman’s. If you work with GraphQL APIs, this matters.
  • gRPC and WebSocket support. Insomnia handles gRPC natively, which Postman added later and with more friction.
  • Plugin ecosystem. Insomnia supports plugins for custom templating, authentication, and themes. Less extensive than Postman’s, but the core ones are solid.
  • Design documents and test suites. The paid tiers add OpenAPI design and automated testing, closing some of the gap with Postman.

Where it grates:

  • The account controversy. In 2023, Insomnia 8 required users to create an account and sync data to the cloud, which sparked significant backlash. Kong later added a “local vault” option and made some account requirements optional, but trust took a hit. If you’re evaluating it, check the current version’s behavior rather than relying on 2023 articles.
  • Collaboration is weaker. Insomnia’s team features exist but aren’t as mature as Postman’s. Real-time collaboration and review workflows are thinner.
  • Smaller ecosystem. Fewer integrations, fewer public collections, less community content.

Verdict: Insomnia is the best pick for individual developers and small teams who want a fast, focused client, especially if you work heavily with GraphQL or gRPC. It’s also a reasonable Postman alternative if you’re willing to pay for the features you’d otherwise get free elsewhere.

Thunder Client: The VS Code Native

Thunder Client started as a simple VS Code extension and has grown into a legitimate API client. Its defining trait is that it lives where you write code.

What works well:

  • Zero context switching. No separate app, no alt-tab. You test an endpoint in a sidebar panel next to your code.
  • Lightweight. Because it runs inside VS Code, it doesn’t add another Electron process to your system. If you’re already running VS Code, the marginal cost is small.
  • Git-friendly storage. Requests can be stored as files in your workspace, which means they travel with the repo and show up in code review. This is a genuinely nice property that neither Postman nor Insomnia matches by default.
  • Scriptless testing. Thunder Client’s testing is more approachable than Postman’s JavaScript-heavy scripts. For basic assertions, it’s faster to set up.
  • CLI and CI support. The paid tier adds a CLI for running collections in CI pipelines.

Where it grates:

  • Limited advanced features. No mock servers, weaker documentation generation, and less sophisticated environment management than Postman.
  • Collection runner limitations. Fine for small suites, less pleasant for large regression runs.
  • Paid tier for team features. The free version is capable for individuals, but collaboration and CLI access require the paid plan (around $5 per user per month at the time of writing).
  • VS Code dependency. If you use JetBrains IDEs or Vim, this tool isn’t for you. There’s no standalone app.

Verdict: Thunder Client is ideal for solo developers, students, and anyone who primarily works in VS Code and doesn’t need team collaboration or heavy automation. It’s the “just enough” option, and often that’s exactly right.

How to Choose

A simple decision framework:

  1. Do you need team collaboration, documentation, and mocking? → Postman
  2. Do you work heavily with GraphQL or gRPC and want a fast standalone client? → Insomnia
  3. Do you live in VS Code and want requests stored with your code? → Thunder Client
  4. Do you need to avoid cloud sync for compliance reasons? → Insomnia (local vault) or Thunder Client (local files), depending on your editor

One more consideration: these tools aren’t mutually exclusive. Plenty of developers keep Postman for team-shared collections and use Thunder Client for quick personal checks. The “which one” question often has a “both” answer.

The Takeaway

There’s no universal winner in 2025. Postman wins on platform depth and team features, at the cost of weight and cloud dependency. Insomnia wins on speed and protocol support, with a smaller ecosystem and a trust deficit it’s still repairing. Thunder Client wins on integration and simplicity, with fewer advanced capabilities.

Pick based on how your team actually works, not on which tool has the loudest marketing. And if you’re unsure, spend an afternoon with two of them on a real project. The friction points show up fast, and they’ll tell you more than any comparison article can.