Getting Started with Mercury

Mercury is a fast, minimal API client for developers who value simplicity. 5MB binary. 50ms startup. Zero monthly fees.

What is Mercury?

Mercury is a native desktop API client built with Rust. Unlike Electron-based tools that consume hundreds of megabytes of RAM, Mercury launches instantly and stays light.

Key philosophy:

• Files, not databases — Your requests are plain .http files you can version control
• No accounts required — Your data stays on your machine
• Keyboard-first — Send requests with ⌘+Enter (Mac) or Ctrl+Enter (Windows/Linux)
• Live sync — Edit in VS Code, see changes instantly in Mercury

Why Mercury over Postman/Insomnia?

Feature	Postman	Insomnia	Mercury
App Size	~500MB	~400MB	5MB
Startup Time	3-5 sec	2-4 sec	<50ms
Memory Usage	300-800MB	200-500MB	~30MB
Account Required	Yes	Yes	No
Price	$14-25/mo	$5-18/mo	Free forever
Open Source	No	Partially	100%

Installation

macOS

Download the latest .dmg from GitHub Releases, open it, and drag Mercury to your Applications folder.

Or build from source:

cargo install mercury

Windows

Download the latest .exe from GitHub Releases and run it.

Linux

Download the AppImage from GitHub Releases:

chmod +x Mercury-*.AppImage
./Mercury-*.AppImage

Or build from source:

cargo install mercury

Your First Request in 60 Seconds

1. Launch Mercury — The app opens with a clean workspace

2. Create a request — Click the + button or press ⌘+N

3. Enter the URL — Type https://httpbin.org/get in the URL bar

4. Send it — Press ⌘+Enter (Mac) or Ctrl+Enter (Windows/Linux)

5. View the response — The JSON response appears in the right panel with syntax highlighting

Quick Start

Want a faster walkthrough? Check out the Quick Start guide for a 5-minute tour.

Interface Overview

Mercury uses a 3-column layout:

Panel	Purpose
Sidebar (left)	Browse your collections and folders
Request (center)	Edit URL, headers, body, and auth
Response (right)	View response body, headers, and timing

Next Steps

• Quick Start — 5-minute guided tour
• Working with Requests — Deep dive into the .http format
• Environment Variables — Use {{variables}} in your requests
• Keyboard Shortcuts — Master the keyboard-first workflow