QR Code Command-Line and SVG Guide for Developers

How do I generate a QR code from the command line?

URL-encode the payload and request PNG or SVG with curl. Save the response as a file and keep a quiet zone around the code when you place it in a document.

curl -G https://qr.lifestep.io/qr \
  --data-urlencode data=https://example.com \
  --data format=png --data scale=6 -o qr.png

# vector output
curl -G https://qr.lifestep.io/qr \
  --data-urlencode data=https://example.com \
  --data format=svg -o qr.svg

Why it works: The payload is encoded into modules: the dark and light squares that a scanner reads. `--data-urlencode` prevents characters such as `&`, `?`, and spaces from changing the query string. Scale controls pixels per module for raster output; SVG is usually better for print or responsive layouts because it stays sharp. Keep strong foreground/background contrast and preserve at least four modules of quiet zone around the symbol.

How do I use a QR code as SVG in HTML without JavaScript?

Put the API URL directly in an `` element. The browser fetches the SVG as an image; no JavaScript, canvas, or QR library is required.

Why it works: A static image request works in plain HTML, server-rendered pages, Markdown-capable systems, and email templates that allow remote images. The `alt` text should describe the destination because a QR symbol is not accessible by itself. For a production site, you may download and self-host the SVG to avoid a runtime dependency; if the payload contains private data, do not place it in a public request URL.

What do QR error correction levels mean?

QR levels trade capacity for recoverability: L restores about 7% of codewords, M about 15%, Q about 25%, and H about 30%. Choose the lowest level that fits the environment, then test the printed result.

# API implementations commonly expose the level as a query parameter
curl -G https://qr.lifestep.io/qr \
  --data-urlencode data=https://example.com \
  --data format=svg --data error_correction=H -o durable-qr.svg

Why it works: Higher correction adds redundant data, so the same payload needs a denser symbol or larger physical size. H is useful for labels exposed to dirt or a logo overlay, but it is not automatically better on a small screen. Quiet zone, contrast, focus, lighting, and physical dimensions matter just as much. Check the API’s supported parameter set before relying on a named option, and scan the final rendered asset rather than only the source SVG.

A small production checklist

Make the command deterministic before putting it in automation. Pin the input hostname or filename, set a timeout, capture the exit status, and emit a concise error that a build log can explain. Treat an empty answer differently from a transport failure: an empty DNS record, a workbook with no matching package member, and an unavailable endpoint are different states. Test one known-good fixture and one deliberately bad fixture so a future dependency or API change cannot silently turn a failure into a pass. Prefer machine-readable JSON when an API provides it, but retain the original command for local diagnosis. If the result controls a user-facing decision, show the reason and a timestamp rather than only a green or red label. These habits keep a useful one-liner understandable when it becomes a scheduled check.