JOSM is an extensible editor for ​OpenStreetMap (OSM) for ​Java 8. It supports loading GPX tracks, background imagery and OSM data from local sources as well as from online sources and allows to edit the OSM data (nodes, ways and relations) and their metadata tags. JOSM is open source and licensed under GPL​.
Launch josm.jnlp (version 19039) recommended version, all platforms, automatic update (if link above doesn't work for you, please read ​Web Start)
Download josm-tested.jar (version 19039) all platforms (how to run)
More options - portable version, mirrors and troubleshooting information

What has been changed recently?

• Startup notes (most important changes)
• Summarized changelog (nicely summarized)
• SVN changelog (very detailed)

Extensions

• Plugins (installation instructions)
• Presets (installation instructions)
• Rules (installation instructions)
• Styles (installation instructions)
• Backgrounds (installation instructions)

Getting Started | Help

• introduction page will guide you during your first edit.
• The official help system / documentation (can be reached with <F1> from within JOSM).
• Ask members of the OpenStreetMap community on
  • the ​OSM-forum
  • OpenStreetMap's ​question-and-answer site
  • various ​OSM mailing lists (e.g. ​talk and ​newbies, ​list overview)
  • the ​OSM IRC channel, including our ​own room

Found a bug? | Have an idea? | Make a suggestion?

• Please report any bug found: Create a new ticket using the Report Bug entry in the main menu Help. Alternatively, the same function is available under About and Show status report.
• Discuss ideas and suggestions also in the bug tracker, on the ​josm-dev mailing list, or on the ​#josm IRC channel.

Contribute

• Use JOSM
  • Report bugs, discuss ideas, think of possible enhancements (see above).
• Participate in bug tracking
  • Review bugs, up/down vote tickets, find duplicates, test bugs, add more descriptive texts.
• Correct/update/extend the online help
  • Unify all JOSM-related Wiki pages and join them with the online help.
• Translate program/documentation.
• Design fancy new icons.
• Write code – get the code and write patches …
  • Source code – get the code
  • See developers guide for build instructions and other details.

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This site

• This site is a combined online help and bug tracking system for JOSM and JOSM plugins.
• No login is required to use this site (neither for reading nor for changes to wiki or bug tracker).
• A login has the following advantages:
  • Mail is sent for changes in your own bug tracker tickets. This is possible by entering an e-mail as user name in the tickets, too, but then be aware that the address is openly visible and you are unable to change that later.
  • Page settings are remembered (e.g. input field size and a lot of other stuff).
• Logins which have no e-mail address or which have not been used at least once are automatically deleted.
• Logins to edit the OpenStreetMap database are separate from the logins on this server.
• Copyright (CC-BY-SA and LGPL since April 2014) of this site is stated in the footer.

Contact

Server sponsored by:

• For problems, ideas, suggestions use the bug tracker.
• The volunteers creating JOSM can be reached using the ​josm-dev mailing list or the ​#josm IRC chat.
• If you use social networks, see our ​Facebook and Google+ pages.