# # Migration Notices

This section lists notable changes that might affect migration:

## # Migration notices for version 7.4.0 - 2020-09-28

UIExtension

- If your UI uses the UIExtension build-in template, and has a custom `tab` in your ribbon toolbar, you should read this change before upgrading. The method for adding custom `tab` was adjusted as follows:

          [{
              target: 'toolbar-tabs',
              action: FRAGMENT_ACTION.APPEND,
              template: '<gtab name="new-tab" group="toolbar-tab" body="new-tab-body">Tab inserted via fragment-configuration</gtab>'
          }, {
              target: 'toolbar-tab-bodies',
              action: FRAGMENT_ACTION.APPEND,
              template: '<div name="new-tab-body" style="line-height:1"><text>New tab body</text></div>'
          }];

- The `<tab>` component was replaced with `<gtab>`. If your UI uses the UIExtension build-in template, the following css should be added:

      .fv__ui-toolbar .fv__ui-gtab-item {
           color: #fff;
       }
       .fv__ui-toolbar .fv__ui-gtab-item.active {
           color: #636363;
           background-color: #fff;
       }

## # Migration notices for version 7.3.0 - 2020-06-29

UIExtension

- The thumbnail component was modularized as an addon in version 7.3. This means you should reference the thumbnail addon at the stage of constructing PDFUI() when upgrading. If don't, you would get a thumbnail loading error . Code example for using addons in PDFUI:

      var pdfui = new UIExtension.PDFUI({
                  viewerOptions: {},
                  addons: [
                  '/uix-addons/thumbnail'
                  ]
              });
              });

- Version 7.3 changed the name of advanced_webViewer to complete_webViewer. If your project use advanced_webViewer directly, make sure you change it to complete_webViewer when upgrading.