Postman vs Insomnia vs Thunder Client: Which API Client Wins in 2025

Three tools dominate the conversation whenever developers argue about API clients. Postman, the long-reigning heavyweight, now bundles AI assistants, mock servers, and team workspaces. Insomnia, acquired by Kong in 2019, has leaned into a design-first workflow and Git-friendly storage. Thunder Client, the newcomer, lives entirely inside VS Code and has quietly crossed millions of installs.

The catch: they’ve converged on features while diverging on philosophy. Postman wants to be your API platform. Insomnia wants to be your spec editor. Thunder Client wants to be invisible. Picking the wrong one in 2025 isn’t about missing features—it’s about workflow friction you’ll feel every day.

Here’s how the three compare on the things that actually matter.

The Contenders at a Glance

	Postman	Insomnia	Thunder Client
Type	Standalone app + web	Standalone app	VS Code extension
Free tier	Generous, cloud-synced	Free for local use	Free core, Pro ~$8/yr
Best for	Teams, API platforms	Spec-first, Git workflows	Quick tests inside the editor
Weakness	Bloat, account friction	Cloud sync limits	No standalone app

Each tool has a distinct center of gravity. Postman is a collaboration platform that happens to send HTTP requests. Insomnia is a REST/GraphQL client with an OpenAPI editor bolted on. Thunder Client is a lightweight request runner that never leaves your IDE.

Postman: The Platform Play

Postman’s advantage in 2025 is breadth. Beyond sending requests, you get:

• API collections and workspaces that sync across a team, with role-based access
• Mock servers generated from examples or schemas
• Automated test suites with the pm scripting API and Newman for CI
• A built-in AI assistant that drafts tests, explains responses, and generates documentation
• Public API network for discovering and forking collections

For teams shipping APIs to external consumers, that’s hard to beat. A backend engineer can publish a collection, a QA engineer can run it in CI, and a technical writer can generate docs—all from the same artifact.

The friction is real, though. Postman pushes you toward a cloud account; local-only usage has become more awkward over time. The desktop app is heavy—hundreds of megabytes and noticeable RAM use. And the free tier’s collaboration limits (three users per workspace at last check) mean growing teams hit a paywall quickly. Postman’s pricing has also drawn criticism: Team plans run roughly $14–$19 per user per month when billed annually, with Enterprise pricing quoted on request.

If you’re a solo developer who just wants to fire off requests, Postman increasingly feels like using a CRM to send a text message.

Insomnia: Spec-First and Git-Friendly

Insomnia’s pitch is narrower and, for some teams, sharper. It treats your API specification as the source of truth. You can design an OpenAPI document inside Insomnia, generate requests from it, and keep the spec in version control.

Key strengths:

• Design-first workflow with an OpenAPI 3 editor and live preview
• Git sync for collections and specs, so changes go through pull requests like code
• Environment variables and templating that feel clean and predictable
• Plugin ecosystem for custom authentication, templating, and linting
• GraphQL and gRPC support alongside REST

Insomnia’s interface is calmer than Postman’s. There’s less upsell, fewer dashboards, and the request builder is genuinely pleasant. For developers who live in Git and care about API contracts, the spec-first model reduces drift between documentation and implementation.

The tradeoffs: Kong’s ownership has shifted the product toward enterprise API management, and some long-time users have complained about pricing changes and account requirements for sync features. Collaboration is weaker than Postman’s—fine for small teams, limiting for larger organizations. The free tier covers local usage well, but cloud sync and collaboration sit behind paid plans (roughly $12–$16 per user per month for team tiers).

Insomnia wins when your team already thinks in specs and Git. It loses when you need org-wide governance, mock infrastructure, or a public API catalog.

Thunder Client: The Lightweight Contender

Thunder Client takes the opposite approach: no standalone app, no cloud platform, no separate account. It’s a VS Code extension that adds a request panel next to your code.

What you get:

• Zero context switching—test an endpoint without leaving your editor
• Collections stored locally in your workspace or globally
• Environment variables, scriptless tests, and basic assertions
• GraphQL support and a CLI for CI pipelines
• Tiny footprint compared to Postman or Insomnia

The appeal is speed. For quick smoke tests during development—checking that a route returns the right shape, verifying an auth header, poking at a local endpoint—Thunder Client is faster than launching anything else. It has millions of VS Code installs, and the free tier covers most individual needs. Pro is inexpensive (under $10 per year), which makes it an easy upgrade.

The limitations are structural. Because it lives in VS Code, it’s tied to that editor—switch to JetBrains or Neovim and it’s gone. Team collaboration is minimal; there’s no shared workspace, no role management, no hosted mock server. Advanced scripting is thinner than Postman’s. And heavy API exploration across dozens of environments gets cramped in a side panel.

Thunder Client is a scalpel, not a Swiss Army knife. That’s the point.

How to Choose

Match the tool to your actual workflow, not the feature checklist.

Choose Postman if:

• You work on a team that shares collections and needs access control
• You publish APIs to external developers
• You need mock servers, automated test suites, and CI integration out of the box
• You’re willing to accept the app’s weight and account requirements

Choose Insomnia if:

• Your team treats OpenAPI specs as the source of truth
• You want Git-based version control for API definitions
• You prefer a focused client over a platform
• You need solid GraphQL and gRPC support without enterprise overhead

Choose Thunder Client if:

• You live in VS Code and want to stay there
• Your needs are individual or small-team request testing
• You value low resource usage and fast startup
• You don’t need hosted collaboration or mock infrastructure

Many developers don’t pick just one. A common pattern: Thunder Client for day-to-day endpoint checks, Postman for team-shared collections and CI, and Insomnia or a dedicated editor for spec work. The tools aren’t mutually exclusive, and the free tiers make mixing them practical.

The Verdict

There’s no single winner in 2025—there’s a winner for your context.

Postman remains the most capable platform, and its AI features and ecosystem keep it ahead for teams that need collaboration at scale. But that capability comes with weight, cost, and account friction that solo developers increasingly resent.

Insomnia is the best choice for spec-driven teams that want their API definitions versioned alongside their code. It’s focused and pleasant, though its collaboration story trails Postman’s.

Thunder Client wins on speed and simplicity. It won’t replace a platform, but for the majority of everyday request testing, it’s the fastest path from “does this endpoint work?” to an answer.

The honest takeaway: if you’re unsure, start with Thunder Client’s free tier inside VS Code. If you outgrow it—shared collections, mock servers, org-wide governance—graduate to Postman. If your team’s real bottleneck is keeping specs and code in sync, Insomnia earns its place. The best API client is the one that disappears into your workflow, and that answer depends entirely on how you build.