The most noticeable difference is the totally revamped administrator, which is updated to a modern design with many simpler and more friendly user-interfaces. Also, Joomla 3.0 is now mobile friendly and can be used with any modern device.
In addition, there are dozens of improvements to the details of all of Joomla, such as a new installer which you will notice when creating a new Joomla 3.0 install. Finally, Joomla 3.0 is packed with goodies for extension developers, such as Bootstrap support and jQuery support.
Launch a 2.5 site if you want the most stable that Joomla has to offer and/or possibly if you plan on using many extensions. Launch a 3.0 site if all the extensions that you plan to use are Joomla 3.0 compatible. Only some template providers or the extension vendors will be ready for Joomla 3.0 at launching, however most will not be ready until days, weeks or months after. (See the “How do I find Joomla 3.0 compatible extensions?” FAQ for more information)
Yes, you will be able to install extensions compatible with Joomla 3.0. The Joomla Extension Directory (JED) will have Joomla 3.0 compatible icons to know which extensions are Joomla 3.0 compatible; however, the best place to check is the developer’s site.
Some template companies will be offering Joomla 3 templates either right away or shortly after release, but you will need to ask each one. Some have already announced that their templates will be ready for Joomla 3 when it is released, but others have not.
Visit Joomla Extension Directory (JED), which will have Joomla 3.0 compatible icons to let you know which extensions are Joomla 3.0 compatible; however, the best place to check is your extension developer’s site.
Extensions that are native to Joomla 2.5 should work on Joomla 3.0 with very little change, if any. Components and templates will need the most work, while modules and plugins should work without issue (assuming they do not use deprecated methods). Extensions that support Joomla 2.5 and 1.5 in the same package will likely not work right away, until the developers update them for Joomla 3 compatibility.
In short, it depends on the extension. The Joomla Project has made the process relatively easy for most extensions, however for some extensions it’s going to take some work. To be certain, let the developers of the extensions know that you want to use their extension on Joomla 3 and consult with their documentation.
You need to speak with the extension developer to see if they have plans to release for Joomla 3 in the immediate future. Developers do have to make some changes but how extensive they are depends on the extension.
In most cases, probably not. Joomla 2.5 will continue be supported until spring of 2014 and you can update directly to Joomla 3 once it’s tried-and-tested thoroughly by other users. You can even wait until Joomla 3.5 which will be released in a year from now and still get a direct upgrade. The only reason you should update is if you need Joomla 3’s features or want to be on the leading edge.
Not unless you’re 1000% sure. By default, Joomla will not let you update to 3.0 unless you activate the option within the Joomla! Update component (administrator >> Component >> Joomla! Update >> Options >> Update server >> Short Term Support). If for some reason you’ve changed this, and you’d like the updater to stop letting you upgrade, change the setting to Long Term Support. After making this change, you’ll only receive updates for Joomla 2.5.
In 6 months, Joomla 3.1 will be released. If you’re on Joomla 3.0, you will need to upgrade to 3.1 at that time using the one-click upgrader. If you’re still on Joomla 2.5, you can continue to wait until Joomla 3.5 and still get a direct upgrade.
Once ready, go to the Joomla! Update component. Click on options and change the setting to Short Term Support. Save. You should be notified of the availability of Joomla 3.0. Click the button to install. Clear your browser’s cache to make sure you see the latest changes. That’s it!
Finally, double check and make sure that everything is working properly.
Note: On some hosts you may need to use alternative update methods such as using the extensions installer.
Support for Joomla 1.5 is officially about to end. Does that mean your 1.5 site will stop working? No, your site will continue to work as it always has. However, Joomla’s developers will not be releasing new versions for Joomla 1.5, so you won’t be getting bug fixes or security fixes. For this reason, it’s recommended to migrate from 1.5.
Moving from 2.5 to any Joomla 3 version is relatively simple, since Joomla has made the process easy for newer versions. Unfortunately, moving from 1.5 is not a trivial task. Fortunately, there are two good extensions that make the process easier: jUpgrade and SP Upgrade.
You have a choice of going straight to Joomla 3.0 or going to 2.5 first. Both SP Upgrade and jUpgrade have versions ready for both versions. Please consult with their documentation on how to migrate from Joomla 1.5 to 3.0/2.5.
Migrate to Joomla 3.0 if all the extensions that you plan to use are Joomla 3.0 compatible. Only some template providers or the extension vendors will be ready for Joomla 3.0 at launch, however most will not be ready until days, weeks or months after. (See the “How do I find Joomla 3.0 compatible extensions?” FAQ for more information)
Migrate to Joomla 2.5 if you want the most stable that Joomla has to offer and/or if you plan on using many extensions.