Galleries and slideshows are just collections of images that can be managed in the Admin Area, before being added to a page.
When adding a new gallery to the Admin Area, you'll need to give it a title and select images to add to the gallery. Selecting one image from the file manager will automatically upload all other images from the same folder. For that reason, it can make things easier if you organise your file manager such that there is a distinct folder for each gallery.
When adding images to the file manager larger images automatically get resized down to a lower resolution which helps increase the page load speed for users when viewing the website.
It is good practice to make sure that images are not larger than they need to be, so if you want to add an image to a section of the website where the image will only be 400px wide, then it is not good to add images at 1500px wide as this will mean the user will have to download a larger image size unnecessarily.
As of v27, when adding images to a gallery you no longer need to worry about the aspect ratio of the images. There is now a feature within the gallery viewer control where you can set the aspect ratio of all the images if required.
Once you've uploaded the images to the gallery, you can modify each image individually to have a caption, link and alt text. You can also modify the order of images in the gallery.
Much like news articles, galleries can be organised into different categories. You have full control over the categories that you make use of.
Top accessibility tips
As with any image on your site, make sure that you include "alt text” on every image in the gallery. Alternative text appears when an image does not load properly and will be read aloud to people using screen readers to access your site.
Alt text should provide a concise but detailed description of the image and is essential for making sure your site is as accessible as possible.