|It is proposed that this informational page become a policy or guideline. Please see the discussion on its talk page or the project chat.
The following is a proposed Wikidata policy or guideline. The proposal may still be in development, under discussion, or in the process of gathering consensus for adoption.
|This page in a nutshell: When merging items, check the subjects are the same, then use the Merge gadget. Do not move the claims manually, otherwise the redirect will not be created. Ask if you are unsure.|
A merge is performed when two or more items exist in Wikidata on the same topic, concept, or object. A merge is a multistep process, first requiring that the collective data about the items be pooled together in one page, or the recipient item, and finally resulting in the redirection of the obsolete page to the new page.
A merge can be done either automatically or manually by moving sitelinks and statements into one item, and then redirecting the obsolete item(s). Automatic merges with the merge gadget are easier to process.
This guide explains how to enable automatic merges by activating the Merge gadget in your preferences or using the Special:MergeItems tool. If this fails, then it also explains the steps to be followed in order to perform a manual merge.
Manual merge: step by step
Check to be sure
Make sure that the items are indeed about the same topic, concept, or object. There could be subtle differences requiring the existence of two or more items.
- en:tree → de:Baum (German word for tree)
- Reason: These are about the same thing (tree) and so should be merged into the (multilingual) item, tree (Q10884)
- en:tree → de:Eichen (German word for oak tree)
- Reason: These are similar but subtly different things and so should remain separate as two items; tree (Q10884) and oak (Q12004), respectively
If you are unsure (for example, due to difficulty translating different languages), or come across items with sitelinks that appear to be inconsistent, it is best to bring up the problem at interwiki conflicts.
Select recipient item
Once it has been decided that two or more items should be merged, one item will be selected to be the recipient item (i.e. the item you are merging to) for sitelinks and statements. The recipient item is usually the item that is used more often (possible indicators are the quality of sitelinks or the number of sitelinks and statements). When in doubt, it's best to choose the item with the lowest Q####, as it will be the older item (meaning the one created before the others).
Sitelinks can be moved manually from one item to another by first removing the link(s) from the obsolete item(s) (i.e. the item(s) you are merging from), and then adding it to the recipient item. If you try to add the sitelink to the recipient item before removing it from the obsolete item(s), there will be a conflict. There is a gadget in your preferences called Move that gives users the ability to move sitelinks quickly. Once the gadget is enabled, go to the obsolete item, select the sitelink you wish to move, click "edit" followed by "move", then input the Q#### of the recipient item.
Move label and description
Correct labels, descriptions and aliases that are present in the obsolete item, but not present in the recipient item, should simply be added to the recipient item. If a different label is already present, you can add the label of the obsolete item as an alias. To check which labels, descriptions and aliases are present in various languages, it is advisable to turn on the labelLister gadget in your preferences. To activate the labelLister gadget for a given item, click on the "Label List" tab at the top right of the item page. Upon clicking on it, you will see a pop-up with a list of all labels, descriptions, and aliases available by language code.
The autoEdit gadget (also under preferences) can in some cases be used to generate new labels and descriptions for the recipient item, which may be easier than moving them from the obsolete item. Once activated, the gadget will appear in the left sidebar menu under "Tools" with the label "Automatic addition."
Correct statements that are present in the obsolete item, but not present in the recipient item, should simply be added to the recipient item. Be sure not to add statements that are already present but keep in mind that it's possible to add multiple values to one property in Wikidata.
Once all the sitelinks, properties, labels, and descriptions have been moved and copied over to the recipient item, the obsolete item can then be redirected. The Merge gadget provides the easiest way to do this. Redirects can also be created using Special:RedirectEntity.
There is also a gadget in your preferences called RequestDeletion that gives users the ability to request deletion quickly. Once activated, the gadget will appear under the "More" tab at the top of an item page.
If you have any questions about merging items, feel free to ask them on the Project Chat.
There are two ways to perform an automatic merge: the Merge gadget or the Special "Merge two items" page.
Please bear in mind, that while automated merges will be terminated if an interwiki conflict is found, you should still always check that the items are the same since the tools simply perform merging that you select to be done.
To enable this function, open Preferences, select Gadgets, check the box for Merge and hit the Save button. To use it, open either the recipient or obsolete item, go to the drop-down menu to the left of "Search" in the top bar (the same place you'll find RequestDeletion), select "Merge it with...", and enter the ID of the other item into the merge wizard. Click on "Merge" when done.
Special:MergeItems can be used to trigger a merge of two items where all labels, descriptions, aliases, sitelinks and statements are moved. Enter the Q#### (not item label) in the fields specifying which is the recipient item ("The id to merge to") and which is the obsolete item ("The id to merge from"). Special:MergeItems does not redirect the obsolete item. If performing a merge with this tool, you will need to follow the create redirect step from the above section on manual merges.
Finding items to merge
Now that you know how to merge, you can make use of your new skill at various places on Wikidata where potential duplicates are found/listed. These places include:
- Wikidata:The Game
- Wikimedia tool which has gamified the merging process, offering candidate pages to potentially be merged by the user
- User:Ivan A. Krestinin/To merge
- lists of merge candidates based on similar page title strings
- lists of merge candidates based on sitelink names being identical
- Commonsmerge and Uniquemerge
- lists of merge candidates based on values of a property being same in two items
- Bene's Lonely Items tool
- finds items containing only one sitelink to a Wikimedia site (which therefore may need to be merged with other items linked to different Wikimedia language versions of the same page)
- Not in the other language
- lists items in a given category that are linked to articles in Wikipedia A but not in Wikipedia B
- Constraint violations
- summary of constraint violations for properties; in particular, "Unique value" violations may indicate a duplication
- Wikidata:True duplicates
- list of items having at least one sitelink which is due to a bug used in another item
Feel free to add any more useful pages or delete ones that are not actively updated!
For related Help pages, see:
- Help:Sitelinks, which explains what sitelinks are and what rules they follow
- Wikidata:Interwiki conflicts, for reporting interwiki conflicts
- Wikidata:Requests for deletions, for nominating items for deletion
- Wikidata:Tools/Gadgets, freely available tools for working with Wikidata
For additional information and guidance, see:
- Wikidata:Project chat, for discussing all and any aspects of Wikidata
- Wikidata:Glossary, the glossary of terms used in this and other Help pages
- Help:FAQ, frequently asked questions asked and answered by the Wikidata community
- Help:Contents, the Help portal featuring all the documentation available for Wikidata