Static vs dynamic QR codes
Almost every question people ask about QR codes comes down to this one choice, and it is much easier to get right before printing than after.
What a static code is
The destination is encoded directly into the black and white pattern. Scan it and the phone reads your link straight off the paper. Nothing sits in the middle, so nothing can break, expire or start charging you.
What a dynamic code is
The pattern encodes a short address belonging to the generator. That address looks up where you want people to go and forwards them. Because the lookup happens on a server, you can change the answer at any time and count how often it was asked.
The trade-off in one sentence
Static buys permanence, dynamic buys control.
When static wins
Wi-Fi codes, contact cards and anything where the data itself is the point. Also anything you expect to outlive your subscription, like an engraved plaque or a code cast into a product.
When dynamic wins
Anything printed at volume, anything tied to a campaign, and anything where you would like to know whether it worked. A wrong link on ten thousand printed flyers is a catastrophe with a static code and a two-minute fix with a dynamic one.
A note on density
Dynamic codes encode a short address, so the pattern is simpler and prints smaller and more reliably than a static code holding a long URL with tracking parameters.
The generator is free and needs no account to preview.
Questions
Can I convert a static code to a dynamic one?
Not after printing. The pattern itself would have to change. Decide before you send anything to print.
Do dynamic codes stop working if I stop paying?
On most services, yes. Look for a provider that keeps existing codes forwarding on the free tier, and keep a record of every destination so you could rebuild if you ever moved.