SmartProxy by Salar Khalilzadeh

Use patterns to automatically define rules for proxify your web experience. With SmartProxy, you don't need to change your proxy manually and turn it on and off. You can add your desired website to the proxy rules list with just one click. After that, when you visit that specific website, SmartProxy will act and all you data for that website will be transferred though the proxy, without you doing anything.

What's more, SmartProxy is inspired by AutoProxy and AutoProxy-ng and that are now considered legacy. SmartProxy is completely written from ground up using WebExtensions and provides same and even more functionality than those proxies.
Important: Due a bug in Firefox 55 any changes require restart. Sorry for inconvenience.

• Automatically detect when to enable or disable proxy to certain websites based on rule patterns
• Easily switch between many proxy servers as your active proxy server setting
• Easily with one click add current site to your proxy list
• View current website items and requests and decide whether to proxify them with one click
• Easily switch between proxy modes and enable proxy for all domains
• Backup/Restore settings and rules

Here is the list of upcoming features

• Sync settings and rules
• Import rules from other proxy extensions
• Adding support to proxy server list

And here is the list of to-do features that currently can't be done due immature WebExtensions API

• Features to enable SmartProxy to be act more smart
• Authentication for proxy servers
• Use system proxy mode

I will do my best to implement these features as soon as the APIs are ready.