Free & Open Source Early Access

The API client
built for developers.

Think Postman — but native, offline-first, and stored in your git repo. No Electron. No account required. No compromise on performance.

Download Free View Source

Windows · macOS · Linux

Instant startup
Single binary
No account required
Offline-first

Everything you need.
Nothing you don't.

Callsmith is built around the principle that developer tools should stay out of your way and let you work.

Native Performance

Built with .NET 10 and Avalonia UI — renders via Skia directly on the GPU. No Electron, no Chromium, no 200 MB runtime. Instant launch and minimal memory usage.

Git-Friendly Collections

Requests are .callsmith files on your disk — plain JSON, readable in any editor. Commit them to your repo, review them in PRs, share them with your team. No import or export dance.

Private by Design

No account. No cloud sync. No telemetry. Your API keys, bearer tokens, and request bodies stay on your machine, full stop. It's open source — read the code yourself.

Full-Visibility Layout

The request editor and response viewer are always on screen simultaneously. Stop switching tabs just to see what your API returned — see everything at a glance.

Powerful Environments

Write {{variable}} in any URL, header, or body. Define values per environment and switch between dev, staging, and production in one click — no copy-pasting secrets.

Searchable History

Every request you've ever sent is stored locally in SQLite. Filter by URL, status code, date, or body content. Find that call from last Tuesday and re-send it instantly.

Import from Insomnia & Postman

Migrate your existing workflow in seconds. Callsmith reads Insomnia export files and Postman collections directly — all your requests, environments, and folder structure come across automatically. No manual re-entry.

Native Bruno Compatibility

Already using Bruno? Point Callsmith at your existing collection folder and open it as-is — no conversion, no re-import, no lock-in. Callsmith reads and writes the same .bru format, so you can switch freely between the two tools without touching your files.

Your data. Your files.
Your tool.

API clients have been drifting toward lock-in for years. Callsmith was built to offer a better path.

Callsmith This is the one
  • No account required — ever
  • Native binary, not Electron
  • Collections live in your filesystem
  • 100% offline — planes, VPNs, air-gaps
  • Open source, MIT licensed
  • Free forever, no tiers
  • Import from Insomnia & Postman
  • 100% Bruno collection compatibility
The Alternatives
  • Sign in just to send a request
  • Electron — heavy, slow to start
  • Cloud sync required for collaboration
  • Features locked behind paid plans
  • Closed source
  • Free tier keeps shrinking

Works wherever you work.

Native builds for every major platform, distributed as a single self-contained binary. Nothing to install — just download and run.

Windows

x64 · ARM64

macOS

Apple Silicon · Intel

Linux

x64

Distributed as a self-contained single-file executable. No runtime or framework installation required.

Ready to craft
better API calls?

Free. Open source. No sign-up. Just download and start sending requests.

Download Callsmith Star on GitHub →