Does the QR code expire, or stop working later?
No. What you get is an image containing your content directly, so there is nothing to expire and no account behind it. That is worth knowing because many free QR generators produce a code pointing at their own short link — which they can then track, rate-limit or switch off. Nothing here goes through a redirect: scan the code and you get exactly the text you typed.
PNG or SVG?
SVG if it is going into a design, a document or anything that will be printed, because it stays sharp at any size — a QR code enlarged from pixels acquires soft edges, and soft edges are what a scanner has to fight through. PNG when you need an ordinary image file: for a message, a slide or a website. Both files here are drawn from the same lattice, so they carry the same code.
Can I put my logo in the middle?
Yes, in whatever you place the image into, and choose error correction H before you do. The correction level is exactly what makes covering part of a code survivable, and H tolerates roughly 30% damage. Keep the covering patch well under that, leave the three big corner squares alone entirely, and test the result with a phone before printing a thousand of them.
Why is my Wi-Fi code not joining the network?
Look at the exact text shown beside the picture — that is what the scanner reads. The three usual causes are visible there: a network set to WPA with no password, a network name that differs from the real one by a space or a capital letter, and a password containing a semicolon, a comma, a colon, a quote or a backslash. This tool escapes those characters, which is precisely the step a hand-written payload misses.
How much can a QR code hold?
Up to about 2,900 bytes at the lowest error correction, and far less as you raise it — but the practical answer is much smaller. Every extra byte adds modules, and a code with more modules has to be printed larger or scanned closer. Put a link in the code and the content behind the link; a whole paragraph encoded directly produces a dense square that a phone struggles to read across a room.
Is my content uploaded?
No. This site is static files and there is no server to send anything to: the encoding, the drawing and the checking all happen in this browser tab. That matters most for the two kinds of content people paste in without thinking — a Wi-Fi password and a personal phone number. Open your network panel, or disconnect after the page has loaded, and the tool keeps working.