Generate a QR code in Ruby

rqrcode

gem install rqrcode (or add it to the Gemfile). Encoding and rendering are two steps:

require "rqrcode"

qrcode = RQRCode::QRCode.new("https://example.com", level: :q)

# vector — the right choice for print
File.write("qr.svg", qrcode.as_svg(module_size: 6))

# raster
png = qrcode.as_png(size: 512, border_modules: 4)
IO.binwrite("qr.png", png.to_s)

level: takes :l, :m, :q or :h — the standard error-correction levels. A detail worth knowing: as_png renders through ChunkyPNG, which is pure Ruby — no ImageMagick, no native extension, nothing to install on the server. border_modules: 4 is the 4-module quiet zone; do not shrink it. For a quick terminal check, puts qrcode.to_s prints the matrix as text.

A Rails helper

SVG inlines cleanly into ERB and stays sharp at any display size:

# app/helpers/qr_helper.rb
module QrHelper
  def qr_svg(data, size: 6)
    RQRCode::QRCode.new(data).as_svg(module_size: size).html_safe
  end
end

<%= qr_svg(ticket_url(@ticket)) %>

html_safe is justified here because rqrcode generated the markup — never apply it to SVG from user input. Generating locally like this is also the right pattern for anything sensitive: WiFi credentials and personal data should not travel to a third party just to become an image.

The keyless API with Net::HTTP

For styled output (colours, module shapes) or typed payloads with server-side validation, the keyless API needs only the standard library:

require "net/http"

uri = URI("https://useqr.app/api/v1/qr")
uri.query = URI.encode_www_form(data: "https://example.com/sale?src=poster", size: 1024)
File.binwrite("qr.png", Net::HTTP.get(uri))

URI.encode_www_form handles the percent-encoding — string interpolation is how payloads containing & get silently truncated. Batch runs can POST /api/v1/qr/batch with up to 100 items per call; larger pipelines are covered in bulk generation at scale. The equivalent Python patterns live on the Python page.

Verify styled output

Round-trip anything you restyle before it ships:

require "json"

uri = URI("https://useqr.app/api/v1/verify")
uri.query = URI.encode_www_form(data: "https://example.com", color: "6366f1")
report = JSON.parse(Net::HTTP.get(uri))
raise report["issues"].join("; ") unless report["scannable"]

The endpoint renders, rasterises and decodes with a real decoder — the decode-verify loop as one GET, easy to drop into an RSpec example or a CI task.

FAQ

What is the standard Ruby gem for QR codes?

rqrcode. It encodes with rqrcode_core and renders SVG, PNG (via pure-Ruby ChunkyPNG) and terminal text with no native dependencies.

How do I show a QR code in a Rails view?

A helper that returns as_svg marked html_safe, called from ERB. SVG inlines into the page and stays crisp at any size and zoom.

Does rqrcode need ImageMagick?

No. PNG output goes through ChunkyPNG, which is pure Ruby, so it deploys anywhere the gem installs — including minimal containers.

How do I set error correction in rqrcode?

Pass level: :l, :m, :q or :h to RQRCode::QRCode.new. Use :h when a logo will overlay the code; :m is a sensible default otherwise.