A QR code (Quick Response) is a two-dimensional barcode invented in Japan. We see these squares of black dots on posters, in magazines, on packaging, in museums and on buildings. Any smartphone camera reads one in a second: modern iOS and Android have a scanner built into the camera app, no separate reader is needed.
How much data fits
What can be encoded? Almost anything. The maximum for the largest code (version 40, level L):
- digits — 7089;
- digits and Latin letters — 4296;
- binary data (including UTF-8 text) — 2953 bytes;
- kanji — 1817.
The more data, the denser and finer the pattern. For print keep the content short, 100–300 characters.
What you can encode
| What | String format |
|---|---|
| Link | https://bl2.ru/ — include the https:// or http:// prefix, otherwise the phone shows plain text |
| Wi-Fi | WIFI:T:WPA;S:MyHome;P:secret123;; — T security type (WPA, WEP or nopass), S network name, P password. The phone connects without typing the password |
| Business card (vCard) | BEGIN:VCARD, VERSION:3.0, N:Smith;John, TEL:+15551234567, EMAIL:john@example.com, END:VCARD — each field on its own line |
| Phone, SMS, e-mail | tel:+15551234567, SMSTO:+15551234567:Text, mailto:info@example.com |
| Location | geo:55.7539,37.6208 |
| Text | any text: an order number, a price, instructions, a coupon code |
Error correction levels (ECC)
A QR code stores redundant data (Reed–Solomon code), so it still reads when part of it is dirty, torn or covered by a logo. The ECC level is the share of codewords that can be restored without data loss:
| Level | Restores | When to choose |
|---|---|---|
| L — Low | ~7% | screens, clean surfaces, maximum data |
| M — Medium | ~15% | general-purpose print |
| Q — Quartile | ~25% | packaging, outdoors, possible dirt |
| H — High | ~30% | logo in the middle, stickers, wear |
The higher the level, the more dots for the same content.
Size and printing
- Size is the image size: pixels per module (dot). 4–6 is enough for screens; for print choose more or download SVG, a vector stays sharp at any scale.
- Distance rule: code side ≈ scanning distance ÷ 10. A business card needs at least 2 cm, a flyer 3–4 cm, a poster read from 2 m at least 20 cm.
- The margin (quiet zone) around the code should be at least 4 modules, otherwise a scanner may not find it.
- Dark code on a light background, high contrast. Not all scanners read inverted colours.
- Test the code with two or three phones before printing a batch.
Where it is used
Links on ads, posters, business cards, T-shirts, vehicles and coupons; payments, e-tickets and boarding passes, restaurant menus, guest Wi-Fi, product labelling and inventory. Also for fun: QR tags on key rings to get lost keys back, coins and CVs with QR codes, city quests where you find a code, get a hint and move to the next level.
How to use the generator
- Type the content: text, a link or a string in one of the formats above.
- Choose the ECC level, size and margin; the code updates at once.
- Download it as PNG (websites, documents) or SVG (print). The code is made in your browser, nothing is sent anywhere.