If you need an online service to crop and resize photos, there are plenty of good options. Fotor is a full-featured photo editor with a variety of cropping and resizing tools, including AI-based options like one-click photo optimization and background removal. It can handle batch photo processing and runs on Windows, Mac, iOS and Android.
Another good option is Pixelhunter, which focuses on AI-based image resizing. It can automatically detect objects and crop images for the best possible resizing for Facebook, Instagram, Twitter and other social media services. That can help you maintain a consistent brand without a lot of work.
If you want to get a bit fancier with your editing, Colorcinch offers AI-based effects to turn photos into art, cartoons and other creative images. It's got one-click background removal, cropping and resizing, too, as well as tools to adjust exposure and color. It's good for personal and professional use.