If you manage a website you will surely need to process your images; resize them, compress them (to make them light and usable by each device), make corrections, or apply a logo, for this there are many easy-to-use software in circulation but only some really respond to criteria of simplicity and effectiveness, let's see which ones.
ACDSee it is one of the most used image viewers, it uses a lot of system resources, allows minor modifications and is paid. Preferable for ease of use, it is in fact one of the most responsive image viewers in its category.
Paid
XnView is a free software for private users, not for companies, which allows you to view, resize and edit your images. Excellent batch image converter, great for transforming groups of images for social media and for your website. Supports over 500 different formats!
Free
JPEGView - Image Viewer and Editor. Slim and fast image viewer with minimal graphical interface. JPEGView is a highly configurable viewer for JPEG, BMP, PNG, WEBP, TGA, GIF and TIFF images with minimal GUI. Basic on-the-fly image processing is provided, allowing you to adjust typical parameters such as sharpness, color balance, rotation, perspective, contrast and local underexposure.
Free
Picasa is a free image editor available for Windows and Mac systems. The software was developed by Google as an alternative to the paid image editors.
It has not received updates since 2016. The program will continue to run on supported platforms, but some features like web album creation have been eliminated. Replaced by https://photos.google.com.
Free