Writing and formatting a tag are not the same thing
Formatting creates the structure a generic reader uses to locate content, and writes an empty message so the tag is valid. Writing puts content into that structure. A tag must be formatted before it can be written, and most tags arrive already formatted.
What formatting does
It writes the capability container, the small area that tells any reader which version of the format applies, how much space is available for content, and whether that content may still be rewritten.
It usually also writes an empty NDEF message, so the tag is not merely described but valid. A formatted tag reads successfully and reports nothing to act on, which is the correct behaviour for a blank tag.
The word is misleading. Nothing is wiped in the sense a disk is wiped, and on a blank tag there was nothing to wipe.
What writing does
It replaces the NDEF message with a new one. The structure stays, the identifier stays, the configuration stays, and only the content region changes.
This is why writing a tag that already holds a URL with a different URL is a single operation rather than an erase followed by a write. The old content is simply overwritten.
Where the confusion causes failures
Three situations, and they present differently enough that people rarely connect them.
A genuinely blank tag, sold unformatted, refuses a write with an error about the format. The tool is correct and the user concludes the tag is faulty.
A tag whose structure was damaged by an interrupted write reads as unformatted even though its memory is intact. Rewriting fails, reformatting succeeds, and only the second is tried by people who know the distinction.
And formatting a tag expecting it to erase sensitive content, which it does, alongside resetting the structure. That one works, and it is worth knowing that a tool offering both operations is not offering the same thing twice.
The right order
Read first, and see what the tag reports. Formatted and empty, formatted with content, or unformatted are three different starting points.
Format only if the tag is unformatted or its structure is damaged. There is no benefit to formatting a healthy tag before writing to it, and on a tag with limited write cycles there is no reason to spend one.
Then write, then read back to verify. The verification step is the one people skip and the one that catches partial writes before they reach production.
Frequently asked questions
Does a new tag need formatting?
Usually not, because most tags ship pre formatted. If a write fails with a format error on a tag straight out of the packet, formatting first is the answer.
Does formatting erase the tag identifier?
No. The identifier lives in a factory programmed area that formatting does not touch, and on a standard tag it cannot be changed by any means.
Can I format a locked tag?
No. Locking makes the memory read only, which includes the structure. A tag locked with damaged content is unrecoverable.
Is formatting the same as erasing?
It has the same effect on content, and it also rebuilds the structure. If your goal is simply to remove what is on a tag, writing an empty message achieves it without rewriting the structure.