Generar código QR
QR Code Generator encodes text, a URL, Wi-Fi credentials or a contact card into a QR code in your browser. The whole encoder — Reed–Solomon error correction included — runs in the page, so the Wi-Fi password you encode is never sent anywhere, and the code has no redirect, no tracking and no expiry.
La interfaz de esta herramienta está en inglés.
La guía de abajo solo está disponible en inglés.
How does QR Code Generator work?
Almost every free QR generator online encodes your data on a server, and a good number encode a redirect through their own domain rather than your URL. That gives them a record of every scan, and it gives them the ability to change where the code points after you have printed it — or to let it expire when a subscription lapses. The QR codes on a restaurant table that stopped working are usually this.
This encoder is ISO/IEC 18004 implemented in the page. Nothing is requested, nothing is sent, and the code points exactly where you said.
Mode selection decides how much fits
Numeric mode packs three digits into ten bits. Alphanumeric packs two characters into eleven, over a 45-character set that includes uppercase letters and a few symbols but not lowercase. Byte mode is eight bits per byte. A URL in uppercase therefore fits in a smaller symbol than the same URL in mixed case — which is why HTTPS://EXAMPLE.COM on a poster is not shouting, it is engineering.
Reed–Solomon is why a damaged code still scans
Error-correction codewords are computed over GF(256) and interleaved with the data, so a scratch or a coffee ring destroys a few codewords from each block rather than one block entirely. That matters because Reed–Solomon corrects a bounded number of errors per block: interleaving is what turns concentrated damage into distributed damage the maths can handle.
Masking is not cosmetic
Data that happens to produce a large blank area, or a run that looks like a finder pattern, is hard for a scanner to lock onto. The spec defines eight mask patterns, and a correct encoder applies all eight, scores each by four penalty rules, and keeps the lowest. That is the difference between a code that scans immediately and one that needs three attempts under a supermarket light.
Error-correction level is a trade, not a quality setting
Higher correction means more redundancy in the same symbol, so either the symbol grows or the payload shrinks. Level M is right for a screen or clean print. Level Q or H is worth the size for a sticker that will be handled, a label that will be outdoors, or a code with a logo placed over the middle — which works precisely because the correction treats the logo as damage.
The quiet zone is part of the code
The spec requires four modules of blank margin. Scanners genuinely need it to find the symbol's edge, and a QR code placed flush against a coloured background or another element is a common reason a printed code fails. The margin is included in the downloaded file rather than left to whoever places it.
Payload
https://toolsbyus.com
Symbol
version 2 (25x25 modules) mode byte level M — about 15% recoverable 21 bytes of payload
What options and edge cases does QR Code Generator support?
| Parameter | Type | Default | Behaviour & edge cases |
|---|---|---|---|
| Level L | error correction | ~7% | About 7% of the symbol can be damaged and still read. Smallest code for the same data. |
| Level M | error correction | ~15% | About 15% recoverable. The usual default, and the right one for a screen or a clean print. |
| Level Q | error correction | ~25% | About 25% recoverable. Worth it for a sticker, a label, or anything that will be handled. |
| Level H | error correction | ~30% | About 30% recoverable. Needed if a logo is overlaid, and for print that will be outdoors. |
| Numeric mode | 10 bits per 3 digits | automatic | Digits only. The densest mode by a wide margin — a phone number barely registers. |
| Alphanumeric mode | 11 bits per 2 chars | automatic | Digits, uppercase A–Z, space and $%*+-./:. An uppercase URL fits in a smaller symbol than a mixed-case one. |
| Byte mode | 8 bits per byte | automatic | Anything else, encoded as UTF-8 — which is what every modern scanner assumes even though the spec nominally says ISO-8859-1. |
| Quiet zone | modules | 4 | The blank margin the spec requires. Scanners need it to find the symbol's edge; a code placed flush against a background is a common print failure. |
| Version | 1 to 20 | smallest that fits | Size is version × 4 + 17 modules. Version 20 at level L holds 858 bytes, which is already past what a phone camera resolves comfortably. |
| Output | SVG or PNG | — | SVG for print — it is resolution-independent and one path element. PNG for anywhere that will not take vector. |
Frequently asked questions
Will this QR code expire?
No, and it cannot. The code encodes your data directly, so there is no redirect, no short link and nothing on any server that could stop working. That is the difference from most free generators, which encode a link through their own domain — giving them scan analytics, the ability to change the destination after printing, and the ability to let it lapse. Restaurant table codes that stopped working are usually that.
Which error-correction level should I pick?
M for a screen or clean print, which is the default everywhere for good reason. Q or H for a sticker, a label, anything outdoors, or anything that will be handled — the redundancy costs you symbol size and buys tolerance for damage. H specifically if you are placing a logo over the centre, which works because the correction treats the logo as damage and recovers from it.
Why does an uppercase URL make a smaller code?
Because alphanumeric mode packs two characters into eleven bits and its 45-character set includes uppercase letters but not lowercase. A mixed-case URL falls back to byte mode at eight bits per character. HTTPS://EXAMPLE.COM/PATH in uppercase can be a noticeably smaller symbol than the same URL in lowercase, and hostnames are case-insensitive so it still works.
Is the Wi-Fi password safe to encode here?
The encoding happens entirely in your browser, so the password is not transmitted anywhere — you can verify that in the Network panel. What the QR code itself does is put the password in a form anyone who photographs the code can read: it is a convenience for a guest network, not a security measure. Print it for guests, not for the network your servers are on.
SVG or PNG?
SVG for anything printed. A QR code is a grid of squares, so it is exactly the kind of thing vector handles perfectly, and it stays crisp at any size — a rasterised code enlarged for a poster develops soft edges that scanners dislike. PNG for a context that will not accept vector, such as some email clients and social platforms.
Why is there a white border I cannot remove?
That is the quiet zone, and the spec requires four modules of it. Scanners use it to find where the symbol ends and the rest of the world begins; without it, detection rates drop sharply. It is included in the downloaded file precisely so it does not get lost when someone places the code against a coloured background.