Here are several good tools you may use for compressing images:
Alternatively you may use the plugin WP Smush.it for automatic image compression while uploading files to media library.
Image optimization - other suggestionsFile format plays the important role
- JPEG - use for photos
- PNG - use for graphics (or not detailed images)
- GIF - use for simple small graphics or images
- BMP/TIFF - do not use them :)
Image resizing with CSS is not accepted by Google
If you use the same image on different sections on your site but its dimension on various pages is not equal then you should crop it as many times as many different dimesions of the same image you use. Why? Using css for changing image dimensions has very bad affect on page loading testers scoring.
Example, do not use the width or height styles for changing image dimensions:
Tons of images on single page affect on page loading
The more heavy images you put on one page the slowest page loading result you will get, simple :)
Someone may ask "What about galleries?" There is a solution, use plugins with lazy loading feature for images.
Use a content delivery network (CDN)
One of many benefits of using CDN is storing the static files like images for example and allow visitors downloading them from the nearer CDN servers.
Check the following free CDN services for your site:
- CloudFlare - offers an WordPress intregration plugin
- Photon - CDN service provided by JetpackJetpack
- SwarmCDN - they have free plan for 10GB of free image delivery