Introducing Napper: CLI-First API Testing for VS Code

API testing tools have a problem. They're either too simple (.http files with no assertions) or too heavy (Postman with its accounts, cloud sync, and paywall). Bruno moved the needle with git-friendly collections, but it's still a GUI-first tool.

Napper takes a different approach.

The CLI is the product

Napper is not a GUI with a CLI bolted on. The command line is the primary interface. Every feature works from the terminal first, then from VS Code second.

# As simple as curl
napper run ./health.nap

# Full test suite with CI output
napper run ./tests/ --env staging --output junit

Plain text everything

Every request is a .nap file. Every test suite is a .naplist file. Every environment is a .napenv file. All plain text. All in your repo. Diffs are readable. Reviews are meaningful.

F# scripting — no sandbox

Most API testing tools give you a sandboxed JavaScript environment with limited APIs. Napper gives you full F# Interactive with access to the entire .NET ecosystem. Parse XML, call databases, generate crypto tokens, run complex assertions — whatever you need.

Get started

Install the VS Code extension or grab the CLI binary from GitHub Releases. Read the documentation to learn more.

Napper is free, open source, and MIT licensed.