If a tag does not scan or write
Nearly every failed read is a tag that moved. Rest the top edge of your iPhone flat on the tag, keep it still for about a second, then tap Try again.
Hex NFC names what went wrong in a sentence rather than showing a code. Find the sentence you saw below. Directly under every failure message sits a closed row labelled Diagnostics, with a chevron at its right. Tap the row and the technical detail opens underneath it.
Find your message
Try these first
Rest the top edge of your iPhone on the tag, not the middle of the back.
Take your iPhone out of a metal case, and lift the tag off any metal surface.
Keep the tag and your iPhone still together until the app answers.
Try a second tag. When the second one reads, the first tag is what to look at.
What does "Scan failed" mean?
"Scan failed" is the heading over a read the app could not finish. The sentence under it names the reason, and the headings below are grouped by it.
Étape 1Open the diagnostics
Tap Diagnostics, the row directly under the message. The detail opens underneath, and the text is selectable so you can copy it out.
Étape 2Start a new scan
Tap Try again. The scan screen opens a new session and waits with "Hold tag against the top of your iPhone".
Étape 3Hold the tag still
Rest the top edge of your iPhone flat on the tag and keep it there until the app answers.
Why did the scan stop part way?
"The scan timed out. Hold the tag steady against the top of the phone and try again. If one particular tag times out every time, it may be a MIFARE Classic, which iPhone can't read (an iOS limitation, not a fault in the tag)."
iOS ended the session because no tag answered it for long enough. Move the top edge of your iPhone slowly over the tag and leave it there.
A tag that starts to answer and then stops gets a different sentence: "Lost the tag mid-read. Keep it pressed against the top of the phone and try again." The tag left the field part way through a command.
"Scan cancelled." means the scan was closed before it finished, either by you or by the app. A scan reads only, so nothing on the tag changed.
Why can my iPhone not read this tag at all?
Three messages say the read cannot happen at all, however the tag is held. A fourth sits here too, and it is not a read failure.
"This looks like a MIFARE Classic tag. iPhone can detect it but can't read its encrypted memory. IOS doesn't expose the MIFARE Classic keys any app would need." The chip answered far enough for the app to recognise the family. It got no further.
"This device does not support NFC." The app could not open an NFC session on this iPhone at all. An iPhone has no NFC switch to turn back on. No setting in Hex NFC changes this. Holding the tag differently will not help. Common questions says what the app needs to run. If the message appears on an iPhone that runs Hex NFC otherwise, open Diagnostics and copy the text. Send it to the address under If you need more help.
"This build isn't authorised for that tag type yet." Your copy of the app is not registered to read that kind of tag. Nothing about the tag or the way you hold it changes that. Check the App Store for an update to Hex NFC first. If the message comes back, open Diagnostics and send the text on to the address under If you need more help.
"This tag does not support that operation." is the message that is not about reading. The tag read. What it will not do is the operation you asked for, by the route you took. The tag info card names the chip. Where the chip reports them, its Supports and Features rows say what it can do.
Operations > Protect with password covers NTAG213, NTAG215, NTAG216 and MIFARE Ultralight EV1. An NTAG424 DNA, a MIFARE Ultralight C and an ICODE SLIX2 take the Protection card on the Tag screen instead. That route protects them properly. Protect a tag with a password walks both routes. Tags that work with Hex NFC covers the chips the app recognises. The chip support matrix has the full technical detail, chip by chip.
What does "Write failed" mean?
"Write failed" is the heading over a write, a read-back or a protection change that did not finish. Three controls sit under it. Diagnostics holds the detail, Close returns you to the editor, and Try again runs the write again, keeping the password you typed. On a write started from the Tag screen that turns protection on or off, the retry reads the tag's UID again. It asks you to type it back a second time. Your consent to change a tag is not carried across a failure. A preset written from Library is not confirmed that way: whichever tag you present is the instruction, so its retry goes straight back to one tap.
Two of the messages have a fix of their own.
"These records are too large for this tag." Your records need more room than the chip's data area holds. Shorten or remove a record, or write to a tag with more memory. Record types says how much room each kind of record takes.
"The tag wrote back something different from what was sent. Try the write again." The app read the tag back after writing and the bytes did not match what it had sent. Tap Try again with the tag held still.
Why was the tag refused after I typed its ID?
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.
"That's a different tag." means the tag you held is not the one the app expected. The Diagnostics row names which tap raised the message, and which tag was expected.
On the Operations screen it comes on the second tap. The tag you held is not the one whose UID you typed. Hold the same tag again, or start over with the tag you meant to change.
A protection change from the Tag screen can raise it on either tap. On the second tap it means the same thing. On the first tap nothing has been typed yet. There the tag you held is not the tag the editor was opened from. Hold that tag instead.
On the Operations screen a failed operation shows the message, then Diagnostics directly under it, then Try again below that. Three screens replace that button because the password you typed is already committed to the run: Protect with password and Attempt limit show Start over, and Remove password shows Enter a different password. Each one hands the form back, so the next attempt sends what you type next rather than the password the tag has just refused.
What if the password check does not finish?
"Couldn't check the password: the tag stopped answering. Hold it steady against the top of the phone and try again." The tag went quiet while the app was checking the password. Nothing was settled about it either way. The app is not telling you the password is wrong. Hold the tag steady and run the operation again. Remove a tag's password covers the password that genuinely no longer opens a tag.
Why does a message say something unexpected went wrong?
"Something unexpected went wrong." appears on the scan screen, the write screen and the Operations screen. It shows when a failure is not one the app recognises as a tag error. "Something unexpected happened. Try again." comes from the NFC layer for the same reason.
Two more describe a tag answering in a shape the app did not expect:
"The tag responded outside the expected protocol."
"The tag responded with data this app could not parse."
All four have the same next move. Open Diagnostics, copy the text, then hold the tag again. When the same message comes back for the same tag, those diagnostics identify it.
If you need more help
The app publishes one address, [email protected], in the Privacy Policy and the Terms & Conditions, both in Settings under Legal. Send the copied diagnostics there, with your iPhone model and your iOS version, which the iPhone's own Settings app shows under General, then About. If the tag read far enough to show a tag info card, add the chip name from it. If it never read at all, say so. Say which tags read and which do not.
Next, read Scan a tag for what a healthy read looks like, or Common questions for what the app needs to run at all.