QR code generator — link, Wi-Fi or contact card

No, and they cannot. The code contains your link or text directly, so there is no redirect service in the middle that could shut down or start charging. Once you download it, it works forever — but it also means the destination cannot be changed later without making a new code.

No. There is no server involved at all. The whole encoder runs in the page you are looking at, so the password is turned into a pattern of squares on your own device and never leaves it. You can disconnect from the internet and the generator keeps working.

M for anything on a screen. Q or H when the code will be printed, especially if it might get scuffed, folded or rained on — those levels can still be read with up to a quarter or a third of the code destroyed. L makes the smallest, least dense code and suits clean digital use.

A common rule is that the code should be at least a tenth of the distance it will be scanned from — about 2 cm for a phone held at arm’s length, and much larger for a poster read across a room. Always leave the light border around the code intact; scanners use it to find the edges.

Yes — set any colour for the code and the background, or make the background transparent. The generator measures the contrast between the two and warns you when a combination will not scan, because scanners tell modules apart by brightness rather than by colour: red on green looks striking to you and is nearly invisible to a camera.

A Wi-Fi network, so guests join without being told the password aloud. A contact card, so a name, phone number and email land in the phonebook from one scan. Plain text works too — a table number, an asset tag, a serial number, a short set of instructions. What a QR code cannot do is carry a file: it holds a few thousand characters at most, so anything larger has to be a link to the file rather than the file itself.

Density is set by how much you put in it. A short link produces a code with large, forgiving squares; the same link with three tracking parameters appended can double the number of modules and make the code noticeably harder to scan at the same printed size. Shortening what goes in is the most effective way to get a cleaner code — followed by lowering the error-correction level, though that trades away the damage tolerance you want on anything printed.

Not with this tool, and it is worth knowing why before you do it elsewhere. A centre logo works only because high error correction can rebuild the modules it covers, so it is spending the same redundancy that protects the code against scuffs and folds. If you do add one afterwards, use level H, keep the logo under about a fifth of the width, and test the printed result with more than one phone — a logo that scans on a new Android often fails on an older camera.

Only if you genuinely need to change the destination after printing, and only knowing what it costs. A dynamic code puts a third party between your customer and your page: if that service shuts down, changes its pricing or is blocked on a corporate network, every code you have ever printed stops working, including the ones already on a wall. A static code like the ones here has no middleman and no expiry, which is the right trade for a menu, a payment page, a Wi-Fi code or a sticker on equipment.

In order: the quiet zone, the contrast, and the size. The light border around the code is not decoration — scanners use it to find the edges, and a code cropped tight to its own squares or placed flush against a dark background often fails outright. Then check that the dark modules really are darker than the light ones; the contrast warning here catches the combinations that look fine to a person and not to a camera. Finally, measure it against the scanning distance: roughly a tenth of that distance is the working rule, so a code read from two metres wants to be about 20 cm across.

Yes, and that is the reason this tool exists rather than being a link to one of the many that would ask you to type the same password into a form on their server. The encoder is JavaScript running in the page you are reading; the password becomes a pattern of squares on your own device and no request carrying it is ever made. Disconnect from the internet and the generator still works, which is the plainest demonstration available.

The QR specification assumes dark modules on a light background. Newer phones often cope with an inverted code, but plenty of stock camera apps only search for the dark-on-light pattern and will simply never see it. If the code has to work on every phone, keep the dark colour on the code and the light one behind it.

When you are placing the code onto a surface you control — a coloured card, a printed flyer, a slide. Whatever sits behind it becomes the background, so keep it light and plain. Dropping a transparent code onto a photo or a dark panel is the fastest way to make it unscannable.

Yes. The largest QR code holds roughly 2,900 characters at the lowest error-correction level, and around 1,270 at the highest. Long text also makes the pattern very dense and harder to scan, so a link to a page is almost always better than the text itself.

Yes. A QR code is just an encoding of your own text — there is no licence, watermark or attribution attached to anything this tool produces. Use them on packaging, menus, business cards or ads freely.