Postman vs Insomnia vs Thunder Client: Which API Client Is Best for Developers in 2025

Three API clients, three very different philosophies. Postman is the 900-pound gorilla with over 35 million registered developers. Insomnia is the design-first challenger now owned by Kong. Thunder Client is the lightweight upstart that lives inside VS Code and has passed 5 million installs.

Choosing between them in 2025 isn’t about which one is “best” in the abstract. It’s about which one fits how you actually work. Here’s a breakdown based on features, pricing, performance, and real-world trade-offs.

The Contenders at a Glance

Feature	Postman	Insomnia	Thunder Client
Platform	Desktop, web, CLI	Desktop, CLI	VS Code extension
Free tier	Generous but cloud-synced	Unlimited local collections	Free with limits
Paid plans	~$14–$49/user/month	~$12–$49/user/month	~$8–$16/user/month
Git-friendly	Partial (newer feature)	Yes (YAML storage)	Yes (JSON in repo)
Best for	Team collaboration, API platform	REST/GraphQL design, privacy-minded devs	VS Code users, quick testing

Postman: The Platform Play

Postman stopped being “just an API client” years ago. In 2025 it’s a full API lifecycle platform: design, mock servers, automated testing, documentation, monitoring, and a public API network.

Where it wins:

• Collaboration. Shared workspaces, role-based access, and comments make it the default choice for teams where QA, backend, and frontend engineers all touch the same APIs.
• Testing and automation. The Collection Runner, Newman CLI, and Postman Flows let you chain requests, run assertions, and wire results into CI/CD pipelines without leaving the tool.
• Ecosystem. Auto-generated docs, mock servers, and integrations with GitHub, Jenkins, and Slack are mature in a way competitors haven’t matched.

Where it frustrates:

• Weight. The desktop app has grown heavy. Startup time on older machines is noticeably slower than the alternatives, and memory usage can climb past 1 GB during long sessions.
• Cloud-first design. Postman pushes you toward signing in and syncing to its cloud. Local-only workflows exist but feel like a second-class path.
• Pricing creep. The free tier is usable, but team features like shared mock servers and advanced roles sit behind the Basic ($14/user/month) or Professional ($29/user/month) tiers. Enterprise pricing is quote-only and, by most accounts, steep.

If your organization already standardizes on Postman, fighting it is rarely worth the effort. The switching cost is real.

Insomnia: The Designer’s Client

Insomnia, acquired by Kong in 2019, built its reputation on a clean interface and a design-first workflow. It handles REST, GraphQL, gRPC, and WebSockets in one window, and its GraphQL support — schema introspection, autocomplete, query linting — remains the best of the three.

Where it wins:

• Git-native storage. Collections are stored as YAML files you can commit, diff, and review like any other code. For teams that want API definitions in version control without exporting and re-importing, this is a genuine advantage.
• Local-first by default. You can work entirely offline without an account. Insomnia only requires login for cloud sync and collaboration features.
• Plugin ecosystem. Community plugins extend authentication, templating, and response handling. It’s smaller than Postman’s, but focused.
• Interface. Developers consistently describe it as less cluttered. Environment switching, request chaining, and the response timeline view are well-executed.

Where it frustrates:

• The 2023 account controversy. Insomnia briefly required accounts even for local use, prompting a community backlash and a fork (Insomnium). Kong walked it back, but trust took a hit.
• Collaboration is thinner. Real-time co-editing and shared workspaces exist on paid tiers but aren’t as polished as Postman’s.
• Smaller community. Fewer tutorials, fewer Stack Overflow answers, fewer pre-built integrations.

The free tier is genuinely unlimited for local work, which makes Insomnia the strongest option for solo developers and small teams who want power without a subscription.

Thunder Client: The Lightweight Contender

Thunder Client takes a different bet: you already live in VS Code, so why open another app? It’s a VS Code extension — under 5 MB, installs in seconds, and keeps your API testing in the same window as your code.

Where it wins:

• Zero context switching. Write a handler, test the endpoint, inspect the response — all without leaving the editor.
• Speed. It launches instantly because it’s not a separate application. On a laptop with limited RAM, the difference is noticeable.
• Git-friendly collections. Requests are stored as JSON files inside your workspace, so they travel with the repo. No export step, no sync service.
• Pricing. The free tier covers most individual needs. The paid tier (~$8/month) is the cheapest of the three and adds team features and CLI support.

Where it frustrates:

• It’s a VS Code extension. That’s the whole pitch, and also the ceiling. No standalone app, no web interface, no mobile.
• Smaller feature set. Advanced scripting, complex test suites, and mock servers are limited compared to Postman. If you need to orchestrate multi-step test flows, you’ll hit walls.
• Team collaboration is basic. Shared collections work, but there’s nothing resembling Postman’s workspace model.

Thunder Client is the right answer when your API work is incidental to your coding work — not a separate job function.

How to Choose

Pick Postman if: you work on a team with dedicated QA, need automated test suites in CI/CD, or want one platform covering documentation, mocking, and monitoring. Accept the bloat and the pricing as the cost of the ecosystem.

Pick Insomnia if: you’re a solo developer or small team that values a fast, clean interface, wants collections in Git, and prefers local-first tools. The GraphQL support alone justifies it for some teams.

Pick Thunder Client if: you spend most of your day in VS Code, test APIs occasionally, and want something that stays out of your way. It’s the best “good enough” option for individual developers.

Consider mixing. Nothing stops you from using Thunder Client for daily poking and Postman for team-shared test suites. Many developers do exactly this.

A Note on What’s Changed

The API client market has shifted in two directions. Postman has moved upmarket into platform territory, which makes it more powerful and more expensive. Insomnia and Thunder Client have moved toward developer-native workflows — Git storage, local-first data, editor integration — betting that developers want tools that fit their existing habits rather than a new hub.

That split is likely to widen. The question worth asking isn’t which tool has the most features. It’s whether you want an API platform or an API tool.

The Takeaway

There’s no universal winner in 2025. Postman remains the safest choice for teams that need collaboration and automation at scale. Insomnia is the best balance of power, privacy, and price for individual developers and small teams. Thunder Client wins on speed and simplicity for anyone whose primary home is VS Code.

Try all three for a week. The right client is the one you stop thinking about — the tool that disappears into your workflow. For most developers, that answer becomes obvious fast, and it usually has less to do with feature checklists than with where you already spend your day.