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Overview

The qr command reads content from standard input (stdin) and generates a QR code that can be scanned with mobile devices. It’s perfect for quickly sharing URLs, text, or data between devices.

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Syntax

echo "content" | ahh qr

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Parameters

This command takes no parameters. It reads all input from stdin.

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Usage Examples

# Share a website URL
echo "https://example.com" | ahh qr

# Share a local tunnel URL
ahh tunnel -p 3000 | grep "Tunnel URL" | cut -d' ' -f3 | ahh qr

# Share a GitHub repository
echo "https://github.com/user/repo" | ahh qr

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Output

The command displays a QR code in the terminal using ASCII/Unicode characters: 
█████████████████████████████
██ ▄▄▄▄▄ █▀█ █▄▄▀▀▀█ ▄▄▄▄▄ ██
██ █   █ █▀▀▀█ ▄█▀█ █   █ ██
██ █▄▄▄█ █▀ █▀▀ ▀▀▄ █▄▄▄█ ██
[... QR code continues ...]

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How It Works

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QR Code Generation

  1. Reads all content from stdin
  2. Generates a QR code containing the content
  3. Renders the QR code to the terminal
  4. Can be scanned by any QR code reader app

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Data Encoding

The QR code can encode:
  • Plain text (up to ~4,296 characters)
  • URLs (automatically recognized by QR readers)
  • Contact information (vCard format)
  • WiFi credentials (special format)
  • Any other text-based data

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Common Use Cases

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Sharing Tunnel URLs

The tunnel and serve commands automatically generate QR codes for their URLs, but you can also manually generate them: 
# Get tunnel URL and create QR
ahh tunnel -p 8000
# QR code is automatically displayed

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WiFi Sharing

Share WiFi credentials that mobile devices can scan to connect: 
echo "WIFI:T:WPA;S:MyNetwork;P:MyPassword;;" | ahh qr
Format:
  • T: Security type (WPA, WEP, or blank for open)
  • S: Network SSID
  • P: Password

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Quick URL Sharing

# Share a local development server
echo "http://192.168.1.100:3000" | ahh qr

# Share a deployment URL
echo "https://my-app.vercel.app" | ahh qr

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Contact Information

vCard format for contact sharing: 
cat <<EOF | ahh qr
BEGIN:VCARD
VERSION:3.0
FN:John Doe
TEL:+1234567890
EMAIL:[email protected]
END:VCARD
EOF

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Technical Details

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Implementation

The command:
  • Uses a QR code generation library
  • Renders using terminal-compatible characters
  • Outputs directly to stdout
  • Supports all standard QR code error correction levels

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Character Limitations

QR codes have size limitations based on version and error correction:
  • Version 1: ~25 characters
  • Version 10: ~400 characters
  • Version 40 (max): ~4,296 characters
Longer content produces larger, more complex QR codes that may be harder to scan.

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Terminal Display

The QR code is rendered using:
  • Unicode block characters for better definition
  • Black and white contrast
  • Automatic sizing based on content length

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Error Handling

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No Input

If run without piped input: 
ahh qr
The command waits for input. Press Ctrl+D to signal end of input.

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Content Too Large

If the input exceeds QR code capacity, the generation may:
  • Fail with an error
  • Create a very large QR code that’s difficult to scan
  • Truncate the content (depending on implementation)
Keep content concise for best scanning results. URLs work well, but large text blocks may be problematic.

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Best Practices

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URL Shortening

For long URLs, consider using a URL shortener first: 
# Better for scanning
echo "https://bit.ly/abc123" | ahh qr

# Harder to scan
echo "https://example.com/very/long/path?with=many&query=parameters" | ahh qr

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Terminal Size

Ensure your terminal is large enough to display the QR code:
  • Maximize terminal window
  • Reduce font size if needed
  • Use a terminal with good Unicode support

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Lighting and Scanning

For best scanning results:
  • Ensure good terminal contrast
  • Avoid terminal transparency
  • Position camera straight-on to the screen
  • Adjust screen brightness if needed
  • tunnel - Automatically generates QR codes for tunnel URLs
  • serve - Automatically generates QR codes for server URLs
  • clip - Copy content to clipboard instead

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Notes

The tunnel and serve commands automatically generate and display QR codes for their URLs, so you typically don’t need to use this command separately for those use cases.
QR codes displayed in the terminal can be scanned directly from the screen using any QR code reader app on a mobile device.

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