Generate a QR Code on Android (Free)

To generate a QR code you need two things: the exact text you want encoded, and a generator that writes that text straight into the pattern. Paste the link, save the image as PNG, and you have a code that works forever — because a QR code is just an encoding of some text, and nothing about it needs a server once the image exists.

On Android, Convertlix's QR Generator does this on the handset: the text you paste is encoded into the pattern locally and nothing is sent anywhere. The scope, up front: Android 8.0 or later, sign-in required (there is no guest mode), a server-set monthly allowance of conversions shown in the app, and output as PNG, JPG or WEBP into Downloads. On the free tier the code is plain black and white — custom styles, colours and a centre logo are Premium. The rest of this page is the part that actually decides whether your code scans.

What you can put in a QR code

The pattern holds text. What makes a code "a Wi-Fi code" or "a contact code" is the format of that text, which phone cameras recognise and act on. The useful ones:

Two things worth knowing before you encode any of these. First, the text is not encrypted — a Wi-Fi code hands the password to anyone who scans or photographs it, which is fine for a café and wrong for your home network. Second, length drives density: a short URL produces a sparse, easy-to-scan pattern, and a 200-character tracking URL produces a dense one that needs real size and print quality to read.

PNG, JPG or WEBP — and why it matters here

This is the choice people get wrong, because for photographs the usual advice is reversed. A QR code is hard-edged black-and-white line art, which is the exact worst case for lossy compression.

JPG's artefacts cluster exactly where contrast changes fastest — the edge of every module — so a JPG code can soften enough at small sizes or low quality that cheaper scanners start failing. It usually still works, which is the problem: it fails on some readers, and you find out from the one person who can't scan your poster. Save PNG and the question never comes up.

Never re-save or upscale a code. Generate it at the size you need. Scaling a raster QR code up interpolates grey into the module edges and is a common cause of "it scanned on my screen but not on the print".

How to generate a QR code on your phone

1. Write out the exact text first. The full URL including https://, or the WIFI:/tel: string from the table above. Open the URL on a phone before you encode it — a perfect code pointing at a dead link is still a wasted print run.
2. Prefer a short URL you control. yoursite.com/menu with your own redirect behind it gives a sparser pattern and lets you change the destination later without reprinting. Make a QR Code That Doesn't Expire (Free) covers why that beats a third-party short link.
3. Open the QR Generator and paste the text. In Convertlix, pick QR Generator, paste, and the code is built on the handset.
4. Save as PNG. The file lands in Downloads. Choose WEBP only if it's going straight onto a website.
5. Keep the quiet zone. The code needs a clear margin of at least four modules — four of the small squares — all the way round. Hand designers the file with that margin already in it, or it gets cropped in the layout.
6. Size it for the scanning distance. The working rule is about 1/10th of the distance the reader will stand at: 3 cm for a 30 cm scan, roughly 30 cm for a poster read from 3 metres. Measure the distance rather than sizing it to look tidy.
7. Test before it ships. Two or three phones, the stock camera app and a dedicated scanner, at final size on the final material. A code that scans on glass and fails on matte card is common and expensive.

Why a QR code fails to scan

Almost every failure is one of five things, in rough order of how often they happen:

• Too small for the distance. The single most common printing mistake.
• The quiet zone was cropped. Works on your phone, fails on cheap scanners.
• Low contrast or inverted. Scanners expect dark-on-light. Mid-grey on white is where trouble starts, and light-on-dark is a coin flip across readers.
• A centre logo that's too big. A logo works because error correction covers the data it hides; past that budget the code silently stops scanning.
• Resaved, upscaled, or screenshotted. Generate at final size from the source.

When this doesn't work

• You need to change the destination after printing. The text is baked into the pattern. Use your own redirect URL, or a dynamic code from a provider and the ongoing dependency that comes with it.
• You need scan analytics. A plain code reports nothing. Your own redirect's server logs are the way to get this without a third party.
• You want a branded or coloured code free. Styles, colours and a centre logo are Premium in Convertlix; free output is a plain code. Stated as the limit it is.
• Payment or ticket codes. Those carry signed payloads from the payment or ticketing system. Never hand-make one.
• Anything private. The text is readable by anyone who scans the code or decodes a photograph of it.
• You're on iOS or desktop. Convertlix is Android-only today. qrencode is free and offline on desktop (qrencode -o code.png -s 8 -l H 'https://example.com').

FAQ

What's the best format to save a QR code in?

PNG, in nearly every case. It discards no pixels, so the hard edges of each module stay exact at any size, which is what scanners read. WEBP in its non-lossy mode is equally good and smaller if the code is going on a website. Avoid JPG: its compression artefacts gather on exactly the high-contrast edges a QR code is made of, and the result scans on most readers but not all.

How big does a printed QR code need to be?

About a tenth of the distance it will be scanned from. Scanned at arm's length, roughly 3 cm across is comfortable; on a wall poster read from three metres, you need around 30 cm. Longer encoded text means more modules and a denser pattern, which pushes the minimum size up further — another reason to encode a short URL.

Can I make a QR code for my Wi-Fi password?

Yes — encode WIFI:T:WPA;S:NetworkName;P:YourPassword;; as plain text and most phone cameras will offer to join the network. The network name is case-sensitive, and T should be WPA, WEP, or nopass for an open network. Remember the password is plainly readable to anyone who scans the code or photographs it, so this suits a guest network rather than your main one.

Do QR codes expire?

The pattern itself never does — it will decode to the same text in twenty years. What expires is a dynamic code, which encodes a short link on a generator's domain and stops working when that trial, subscription or company ends. A code with your URL written directly into it has no service behind it to switch off.

Does Convertlix upload my link?

No. The code is generated on the phone from the text you paste, and nothing is sent anywhere — the app's network calls carry identity, licence, quota, configuration and payment data, never your content. Sign in once, turn on airplane mode, and the generator still works.

Is there a free way to generate a QR code without installing anything?

Yes. qrencode is free, open source and runs offline on desktop, and Python's qrcode library does the same in two lines — both give you direct control over error correction and module size. Plenty of browser-based generators are free too; the ones to be careful with are those requiring an account or offering to edit the destination later, because those are dynamic codes that depend on the provider staying in business.

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Write out the exact text, encode it, save it as PNG at the size you actually need, and test it on the final material before it goes anywhere expensive.