a couple of Free Mac Utilities for your delight.. (Mac OS only — won’t work on iPhone/iPad.)

Photopage is a Photo Gallery Maker Utility for a webpage

Turns a folder of photos (and short video clips) into a simple, self-contained web page gallery –> a thumbnail grid with an adjustable size slider and a click-to-enlarge view with arrow navigation, similar to Apple’s old iPhoto which could web page export that produces a folder you can upload to your server with all your photos together with an index page.(download here)
ps
if you want to prepare your image files before running Photopage, easiest way is, if you are in photos on mac, export to folder and choose your size format compression etc
but
if you have a mixed folder of images jpegs pngs and some are big and you want to make them smaller try our Optoimage utility that batch edits them, reduces stuff over 500k and produces jpegs from bigger pngs — you can output as a single total folder or a folder that has only the changed files (remember though that the bigger pngs would remain in your original folder, so if you added the changed files you’d duplicate the pngs
nice wee app it is (download here)

Both Utilities are only for Mac OS (desktops & Laptops) not for IOS phones & tablets 

ps — after unzipping, open the ReadMe first — it covers the Mac security warning thing regarding installs not from their App store