"Hi, I would like to book..." is the sample message in the form above, and a message like it is the part that makes an email QR code too dense for a business card. The address alone, mailto:hello@example.com, is 24 bytes and a 25 by 25 grid. Add the subject "Table for two" and it grows to 50 bytes and 33 by 33. Add a 96-character booking request as the message and it reaches 194 bytes, a 57 by 57 grid that needs at least 26mm of print width. On the 20mm Business card preset, each square shrinks to 0.31mm, under the 0.4mm floor the sizing panel checks, and the panel says so.
What the code contains. The generator writes a mailto: address, the format set out in RFC 6068: the address, then subject= and body= when you fill those in. Spaces become %20, and characters such as the ampersand and hash are percent-encoded so a scanner can't mistake them for the structure of the address. The email address itself is written exactly as you typed it.
What the phone does. A scan opens the phone's mail app with a new email to you. RFC 6068 says a mail app should not send a message from one of these addresses without first showing it in full and asking for approval, so the person scanning gets a draft. They can change the subject and message before they send it.
Use the subject to tell codes apart. UTM tags only work on web addresses, and an email code opens a mail app, so web analytics never sees the scan. The subject line can do that job instead. Give each placement its own subject, such as "Enquiry: window poster" and "Enquiry: counter card", then search your inbox for each one. People can edit the subject, so treat the counts as a minimum. If you would rather send people to a web form, make a Link code and tag it using the QR code UTM builder.
Before you print. Pick a preset in the sizing panel (Business card, Table tent, Poster or Yard sign) or drag the width. The panel shows the grid, the size of each square and how far the code should scan from, roughly ten times its printed width. Keep the Square pattern for anything printed, because the rounded styles change the three corner markers that stricter scanners look for. Adding a logo raises error correction to Q automatically, which makes the grid denser again, so check the panel after you add one. QR code best practices for print covers contrast, finish and the clear margin.
To see the exact text inside the finished code, drop the PNG into the QR code reader. To hand over your name, number and address in one scan, the digital business card maker puts them all in a contact card. The main QR code generator makes link, Wi-Fi, phone, SMS and text codes with the same controls.