"But it's true!" is not a sufficient reason to keep information on Wikipedia.
When submitting new articles to Wikipedia, or adding content to existing ones, you may be surprised if some or all of that content is reverted by another editor, or, in the case of new articles, the article is deleted. While newer editors are the ones most commonly surprised by this, even experienced editors can be caught off-guard when their contributions are removed. This is especially true when the editor has taken great care to ensure the content provided was true. This essay is intended to help you understand why this might happen, and how to best handle the situation when it does.
Reversion is a normal part of the Wikipedia editing process, and should not be taken personally. The overwhelming majority of reverts are done in good faith. It is also likely that even when the other party disagrees with your edit, they believe you were acting in good faith as well. To understand why an edit was reverted, start by reading the edit summary on the revert, if one was provided. The summary might provide important clues as to the reason, perhaps by citing one or more policies or guidelines, or by referring you to the article's talk page.
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Core content policies[edit]
Accuracy is important to any encyclopedia. For this reason, Wikipedia has developed three core content policies. Each of these policies functions much like one leg of a three-legged stool or table. Leave off any one of the legs, it will fall. Likewise, any edits that do not meet all three of these policies are likely to be challenged or removed. It is not enough to meet just one or two of them.
Neutral point of view (or WP:NPOV)[edit]
All encyclopedic content on Wikipedia must be written from a neutral point of view, without bias, representing significant views fairly, accurately, and in due proportion to the prominence of each viewpoint. Wikipedia aims to describe disputes as represented in reliable sources, but not to engage in such disputes.
Editors naturally have their own points of view, but should strive in good faith to provide complete information and not to promote one viewpoint over another. Use non-judgmental language, neither sympathizing with or disparaging subjects. Where controversies exist, accurately indicate the relative prominence of each opposing view.
Verifiability (or WP:V)[edit]
One way we promote accuracy on Wikipedia is to provide a means for readers (and other editors) to independently verify the accuracy of our content. We do this by citing reliable sources. Unsourced or poorly sourced contentious material about living persons—whether the material is negative, positive, or just questionable—is especially likely to be removed, even if the material appears on a page other than that person's biography. Personal knowledge, anecdotal experience or hearsay are not acceptable unless they can be somehow be verified with a reliable source. We don't necessarily doubt that what you are writing is true, but if we cannot verify it then it does not belong in the article.
If an edit was removed because it did not cite a source (or did not cite a reliable source), try to find one. If your source is considered unreliable and you're not sure why, try asking politely for clarification on the article's talk page. Most editors will be happy to help.
No original research (or WP:NOR)[edit]
Like any encyclopedia, Wikipedia is not a publisher of original research or original thought. Rather, its purpose is to collect and provide an overview of knowledge that has been published in other reliable sources.
Perhaps you know something is true, because you were there when it happened. That's great, but unless it's been written about in a reliable source, it's an example of original research, which is defined in part as "material for which no reliable source can be found." To show that your edit is not original research, you must be able to cite a reliable source that contains the same information. If you can't do that, then your edit constitutes original research, and is not appropriate for inclusion in an encyclopedia.
A more subtle form of original research is synthesis, which is drawing a conclusion by combining facts from multiple sources. As an example, suppose you have one source that says all ratchets are widgets, and another source which says all widgets are gadgets. It might seem obvious from this that all ratchets are gadgets, but such a statement would be synthesis. To include a statement that all ratchets are gadgets, you must find a reliable source that draws the same conclusion.