Question 1

Why does my code look different every time I change the error correction level?

Accepted Answer

Because each level rebuilds the code's internal structure, not just its appearance. Level L reserves roughly 7% of the data cells for Reed–Solomon error-correcting codes, and H reserves about 30%, so raising it leaves less room for your actual content at the same version and can push the whole code up to the next size to fit. There is no version where changing the level does nothing.

Question 2

Which error correction level should I use?

Accepted Answer

M is the reasonable default and what most generators ship with. Go up to Q or H when the code will be printed small, laminated, or placed somewhere it might get a logo overlaid, a corner torn, or a bit of glare across it, such as a business card or a product label. Stay at L when the content is already long, like a full URL with tracking parameters, and you'd rather keep the code smaller and easier for a camera to focus on than add redundancy it may not need.

Question 3

Will any phone actually scan the Wi-Fi and contact codes?

Accepted Answer

The current Camera app on iOS and Android reads every mode without installing anything: point it at the Wi-Fi code and it offers to join the network with the password already filled in, at the contact code and it offers to save it, at the event and it offers to put it in the calendar. That behavior comes from the phone recognizing the WIFI:, vCard and VEVENT formats, not from anything specific to this tool, so a code made here reads the same as one made by any generator that follows the same formats.

Question 4

Why did generating fail with a message about too much data?

Accepted Answer

A QR code has a hard ceiling on how many characters it can hold, and that ceiling depends on both the version (there are 40, each larger than the last) and the error correction level you picked. At the highest version and lowest level (L) it tops out around 4,296 alphanumeric characters or about 2,953 bytes; at the highest level (H) that drops to roughly 1,852 characters. A long vCard with a note field, or a URL stuffed with tracking parameters, can cross that line. Dropping to error correction level L or trimming the text usually fixes it.

Question 5

What's the difference between the PNG and the SVG download?

Accepted Answer

The PNG is a fixed grid of pixels at the size you set, which is what most printers, chat apps and slide decks expect. The SVG describes the same modules as vector shapes, so it can be scaled up to poster size or dropped into a design tool without ever showing a jagged edge. That matters for anything printed larger than a business card, where a raster export made small and then stretched turns visibly blocky.

Question 6

Can I use any two colors for the code?

Accepted Answer

A scanner reads a QR code by thresholding it into light and dark, so the two colors have to be far enough apart in brightness for that to work. A mid-gray on a slightly lighter gray can fail even though it looks perfectly readable on a bright screen. Rather than guess, the tool decodes the finished image and tells you which side of the line you landed on. The safest choice is still a dark code on a light background, not the reverse, because ink spread and glare on paper behave differently from a backlit screen.

Question 7

Can I put my logo in the middle without breaking the code?

Accepted Answer

Usually yes, and the reason is error correction rather than any spare space in the middle. A QR code carries Reed–Solomon codewords that let a reader rebuild data it could not see, so a logo that covers part of the grid is just damage the code was built to survive. Adding a logo here switches the level to H, which tolerates around 30%, and the size slider is capped at 40% of the width. Since covering area rather than width is what costs you, a logo a fifth of the width hides about 4% of the code while one at 40% hides 16%.

Question 8

What does the check under the preview actually do?

Accepted Answer

It draws the code once more off screen and runs it back through a QR decoder, then compares what came out against what you typed. That is a different thing from the contrast or coverage warnings most generators show, which are guesses about whether a scanner would cope. Here the design you built, logo and colors and shapes included, has already been read once. In Batch every row is checked, not only the one being previewed, because rows of different lengths land on different code sizes and a logo that survives the first can still swamp the fiftieth.

Question 9

How large does the code need to be printed?

Accepted Answer

The figures under the preview work it out from the module count rather than from the pixel size, since pixels mean nothing until a DPI is fixed. The rule is a floor on how small one module can get: about 0.4mm before a phone camera struggles to resolve it, and 0.5mm is the width most printers hold without ink spread closing the gaps. A denser code has more modules, so it needs more millimetres. As a rough guide it reads from around ten times its own width away.

Question 10

Why are there fewer corner shapes than on some other generators?

Accepted Answer

Because the ones left out did not survive being decoded. A reader finds a QR code by scanning for the 1:1:3:1:1 run of dark and light that a finder pattern produces, and that ratio has to hold on the diagonal as well as across. A diamond centre breaks it, and so does a square centre inside a circular ring, whose diagonal runs 4.24 units against the ring's 3. Both were built, tested at every size, and dropped. What is offered here is the set where all sixty combinations of module, frame and centre read back correctly.

Question 11

Can a QR code hold a crypto payment?

Accepted Answer

Yes, and it is the original use for these URI schemes rather than a novelty. Bitcoin, Litecoin and Dogecoin use BIP-21, the bitcoin:address?amount= form wallets have read since 2012. Ethereum uses EIP-681, which carries the amount in wei, so 0.1 ETH is written as 100000000000000000. That conversion runs on whole numbers here rather than on decimals, because at eighteen places ordinary arithmetic starts rounding: 1.1 ETH through a float lands on 1100000000000000100 wei. Check the address against your wallet before printing, since nothing in a generator can tell a mistyped address from a real one.

Question 12

Is the “SCAN ME” caption worth adding?

Accepted Answer

On anything people walk past, yes, and it is the cheapest change on the page. A bare square on a poster or a table tent asks someone to work out both what it is and what happens if they point a phone at it. A caption answers the first question and a frame draws the eye to it. Where the code sits in a context that already explains itself, such as a link on a slide or an invoice, it is just clutter.

Question 13

Can I make a lot of codes at once?

Accepted Answer

The Batch mode takes up to 200 lines and returns them as a ZIP, with every code carrying whatever design you set and every one decoded back before it goes in. Anything that did not read is named for you and still included, so the set stays complete and you can fix the design rather than hunt for the missing row. Put a name and a comma in front of a link and that becomes the file name, so a two-column spreadsheet pasted straight in comes out as Table 12.png rather than qr-7.png.

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