Wikipedia:Verifiability challenges

You may not restore unsourced material to an article after it has been WP:CHALLENGEd, unless you provide an inline citation to a reliable source that supports the material.

What is a challenge?

A verifiability challenge is any good-faith claim that unsourced material cannot be verified in any reliable source.

What is not a challenge?

If the dispute's primary locus is something other than a good-faith question about whether a published reliable source contains this information, then it is not a verifiability challenge. This includes all disputes about neutrality, unencyclopedic content, writing style, level of detail, which article the material is best suited for, and much more. Although providing good sources solves many of those disputes, they are not challenges to the material's verifiability.

How do you know if material has been challenged?

Material has been challenged if someone expresses a concern about the information being unverifiable, original research, or factually wrong. Common ways of doing this include adding templates such as {{fact}} or using edit summaries that say something such as "Remove unverifiable content" or "I think this is original research". If another editor removes information without providing a reason, but in your judgment, the likely reason for the material's removal is a concern about the material's accuracy or verifiability, then you should treat that material as if it had been explicitly challenged.

The other editor said "Removing errors", but I know the editor is wrong! Do I really have to provide a source?

It doesn't matter if you believe that the other editor is wrong. If you restore it to the article, then you have to provide an inline citation.

So if I say "I CHALLENGE this material", can I blank unsourced material on every page I encounter?

No. Bad-faith removals, including vandalism and WP:POINTY disruption, are not subject to this policy.

I challenged some unsourced material, and another editor restored it with a poor source. Now what?

When you challenge unsourced material, the obligation on the other editor is only to cite one source that the other editor – not anyone else – believes to be acceptable. If you think that the source provided is unreliable, then you may provide a better one yourself. If you don't believe that any reliable source has ever been published for this material, then you may want to discuss it on the talk page or at Wikipedia:Reliable sources/Noticeboard.