File -> Update Data (Ctrl U)

File->Update data reloads all bounding boxes in the currently active data layer from the server.

(This action is disabled unless the currently active layer is a data layer.)

You should run File->Update data if you like to refresh the data in the current data layer with the data the server currently holds. Your local edits will not be deleted by this update! Here is how it works:

Objects, you added or edited, will not be affected by the update. If there are new objects on the server (created by other users in the meantime) they will be added to your layer (and thus merged with your own work). If the server reports objects, that have changed (i. e. a node was removed from a way or a tag was added to an object), these changes will be applied to your local layer, unless you changed one of these objects as well.

In short: If two users edit one area at the same time, JOSM tries to merge both versions. If this is not possible it will create conflicts.

You will have to resolve these conflicts manually after the update is finished.

Example: Imagine you find a way that looks strange and you add the tag 'FIXME=please check this'. But in the meantime someone else spotted the same error, added the tag 'FIXME=does this way exist?' and uploaded it. Then you click update to get the latest version from the server. In this case JOSM cannot decide which of the changes to keep, so it will create a conflict.

Note:

• You can't avoid conflicts by not updating the data! They will just show up at a later time (when uploading).
• Updating has the same effect as downloading the area again (Download as new layer unchecked).

See also

• Update selection
• What is a conflict?