Postman vs Insomnia vs Thunder Client: Which API Testing Tool Is Best in 2025
Every API developer eventually faces the same decision. You need a tool to send requests, inspect responses, manage environments, and maybe run a few automated tests—and three names keep coming up. Postman, the industry heavyweight. Insomnia, the design-first challenger. Thunder Client, the lightweight upstart living inside VS Code.
The choice matters more than it used to. Postman now pushes hard toward team collaboration and API governance. Insomnia has been rebuilt under Kong’s ownership. Thunder Client has matured from a weekend project into a serious contender. Here’s how they compare in 2025.
The Contenders at a Glance
| Feature | Postman | Insomnia | Thunder Client |
|---|---|---|---|
| Pricing (individual) | Free tier; paid from $14/month | Free tier; paid from $12/month | Free tier; paid from $8/month |
| Platform | Desktop, web, CLI | Desktop, CLI | VS Code extension |
| Git sync | Paid plans | Free (Git Sync) | Limited |
| Open source | No (core is closed) | Partially | No |
| Best for | Teams, enterprise | Individual devs, API design | VS Code users, quick tests |
Prices reflect published individual plans as of early 2025 and change frequently, so verify current rates before committing.
Postman: The Ecosystem Play
Postman is less a tool than a platform. It handles REST, GraphQL, gRPC, WebSocket, and SOAP requests, and wraps them in a collaboration layer that few competitors match. Collections, workspaces, mock servers, monitors, and a public API network all live in one place.
The strengths are real. If your team needs shared environments, role-based access, and API documentation generated from the same collections you test with, Postman does it out of the box. The Postman CLI and Newman let you run collections in CI pipelines, which makes it a genuine part of a delivery workflow rather than just a debugging toy.
The friction is equally real. Postman has grown heavy—launch times and memory usage are common complaints. More significantly, the company has pushed collaboration features behind paid tiers, and the free plan now limits some of what individual developers once got for nothing. Git-based version control requires a paid plan, which frustrates teams that want their API definitions in the same repo as their code.
Verdict: Still the default for teams and enterprises. Individual developers may find it overkill.
Insomnia: Design-First and Developer-Friendly
Insomnia built its reputation on two things: a clean interface and native support for API specification formats like OpenAPI and GraphQL. You can import a spec, generate requests from it, and iterate on the design without leaving the tool.
Kong acquired Insomnia in 2019, and the product has since added a CLI, a mock server, and expanded protocol support including gRPC and WebSocket. Git Sync remains available on the free tier—a meaningful advantage over Postman for solo developers who want version control without a subscription.
Insomnia’s design-first orientation appeals to developers who think about APIs before they build them. The scratchpad and request chaining features feel purpose-built for exploration rather than enterprise process.
The trade-offs: Insomnia’s plugin ecosystem is smaller than Postman’s, its collaboration features are thinner, and some users have grumbled about the account requirements Kong introduced. It’s a strong individual tool that hasn’t fully matched Postman on team workflows.
Verdict: The best balance of power and simplicity for individual developers and small teams.
Thunder Client: Lightweight and In-Editor
Thunder Client takes a different approach entirely. It’s a VS Code extension, not a standalone app. That means no context switching—you write code in one pane and fire off requests in another, with the same keyboard shortcuts and theme.
The appeal is speed. Installation takes seconds. There’s no account requirement for basic use, no telemetry-heavy onboarding, and no separate app eating RAM. For quick endpoint checks during development, it’s often faster than opening Postman at all.
Thunder Client supports collections, environments, and a CLI for CI runs, and it handles the essentials—REST, GraphQL, authentication helpers, and test scripts. It has grown well beyond its minimalist roots.
The limits show up at scale. Team collaboration is minimal compared to Postman. Deep testing and scripting are less capable. And if you don’t use VS Code, it’s a non-starter—there’s no standalone version. It’s a complement to a full-featured tool as much as a replacement for one.
Verdict: Ideal for VS Code users who want fast, low-friction testing without leaving the editor.
How to Choose
The right answer depends on your context, not on which tool “wins.”
Choose Postman if you work on a team that needs shared collections, generated documentation, and CI integration—and you’re willing to pay for the collaboration features that make it worthwhile.
Choose Insomnia if you’re an individual developer or small team that values API design, wants free Git sync, and prefers a lighter interface than Postman’s.
Choose Thunder Client if you live in VS Code, mostly test endpoints during development, and want zero overhead. Many developers run it alongside one of the others.
A practical note: these tools aren’t mutually exclusive, and switching costs are low for basic use. You can export collections between them in most cases. The bigger commitment is where your team’s shared API definitions live—that’s the decision worth deliberating.
The Bottom Line
There’s no universal winner in 2025. Postman remains the most complete platform and the safest choice for teams, but it’s no longer the obvious pick for individuals. Insomnia offers the best design-first experience with genuinely useful free features. Thunder Client wins on speed and simplicity for anyone already in VS Code.
Pick based on your workflow: team size, whether you need version-controlled specs, and how much you value staying inside your editor. Then revisit the decision in a year—all three tools are evolving quickly, and the gap between them keeps shifting.