Limit wrong password tries
An attempt limit tells a password-protected tag how many wrong passwords to take. Set it to 3, and the tag accepts three wrong tries; the try after that stops it accepting its password at all. From then on the protection can never be removed, and the protected memory can never be rewritten. There is no way back.
Before you start:
The tag has to be password-protected already.
You need the password it holds now.
The chip has to be an NTAG21x or a MIFARE Ultralight EV1, which is where this field lives.
To see what a chip carries, read Tags that work with Hex NFC or the chip support matrix.
The limit is not part of the Protection card. It sits on the Operations screen, under Dangerous Actions, because it is armed against one tag at a time and cannot be undone.
A change to a tag's protection holds the tag twice, and so does every operation under Dangerous Actions. The first tap reads the tag's UID and closes straight away, so you can type. The app then asks you to type that UID back, character for character, and the second tap makes the change on the tag you confirmed. Present a different tag on the second tap and the app refuses it rather than changing the wrong one.
The scan that opens the tag is not one of those two taps. Here you tap the tag three times in all: once to scan it, then the operation's two taps.
Set the attempt limit
Paso 1Scan the tag
In Hex NFC, on the home screen, tap Scan, then hold the tag against the top of your iPhone. What the tag holds opens on the Tag screen. The card at the top is headed with the chip's name. The Protection card sits directly under it, above the records.
A tag whose password gates writing only scans like any other. Its Protection card reads "Password · write-only".
A tag whose password also gates reading stops the scan instead. The scan screen shows "Tag is protected" and asks for the password. Enter it, then tap Unlock & scan again. The Tag screen opens after that, and its Protection card reads "Password · read + write". That unlock presents the password to the tag, so a wrong entry spends one of the tries this page is about. Scan a tag covers the unlock in full.
Paso 2Open the attempt limit screen
On the Tag screen, tap the menu button at the top right, beside Write, then tap Operations…. On the Operations screen, tap Attempt limit in the Dangerous Actions card.
Paso 3Enter the password the tag holds now
Enter the tag's password in Current password (4 bytes), as hex, with or without
:separators.Paso 4Choose how many wrong tries to allow
The row reads Allow 3 wrong tries, and its number changes as you press the stepper beside it. Choose any number from 1 to 7. It starts at 3. The stepper has no setting for none, so this screen can change the limit a tag carries but never take it off. Removing the tag's password clears the limit with it, which needs a password the tag still accepts.
Paso 5Tap Continue
Tap Continue. The password field and the stepper stop taking changes, and the screen asks for the first tap.
Paso 6Hold the tag for the operation's first tap
Tap Set the attempt limit, then hold the tag against the top of your iPhone. This tap reads the tag's UID and the limit the tag is already set to.
Paso 7Type the tag's UID
Type the UID shown on the screen into the field beside it.
Paso 8Hold the same tag for the second tap
Tap Set the attempt limit, then hold the tag against the top of your iPhone again. The app writes the new limit and reads it back. The screen reports "This tag is now set to allow 3 wrong tries."
Below that it adds "One more wrong try after that and it stops accepting its password for good."
What the app reports between the taps
The first tap reads the tag's own settings, so the screen says what the tag carries before you type its UID. It reports one of three things:
"This tag has no attempt limit set." No number of wrong tries can lock it.
"This tag is already set to allow 3 wrong tries." The number is the one the tag holds, and the new limit replaces it.
"This tag is read-protected, so the limit it holds now can't be read until its password is presented." There is nothing to report. The configuration pages are behind the password. The run carries on from here: type the UID, and the second tap presents the password and writes the new limit.
How many tries a tag has already spent is never reported, because no command on these chips discloses it.
If the tag has no password
An attempt limit guards a password, so the app refuses the operation on a tag that has none. The refusal reads "This tag has no password set, so there is nothing for an attempt limit to guard."
The refusal comes before anything is written. The tag is left exactly as it was. Set a password first, as Protect a tag with a password describes, then come back here.
If the app cannot read the limit back
A tag that slips away mid-write gets the headline "Attempt limit written."
The explanation reads "The tag acknowledged the write, but this tap couldn't read the byte back. Start the operation again: the first tap reports the limit the tag is holding." The chip took the write. This tap could not prove what landed.
The run has finished at that point, so the screen offers no retry. Go back to the Operations screen and open Attempt limit again. Run it through: the first tap of the new run reports the limit the tag is holding.
If a password stops working afterwards
On a tag with a limit set, a password the tag refuses is reported as "The tag refused that password. This tag has an attempt limit set, so it may be locked out even if the password is right."
A check that never finished reads "That password didn't open the tag. This tag has an attempt limit set, and every wrong try counts against it. Check the password before trying again."
Both mean the same thing for your next move: find the right password before you hold the tag again. A run that ends this way leaves Start over on the screen, which hands the form back rather than sending the refused password a second time. Once a tag has had more wrong tries than it allows, nothing opens it, and its protected memory stays protected for good.