What are some alternatives?
When comparing Search by Image Extension and SauceNAO, you can also consider the following products
TinEye - Reverse Image Search to help find an image's source, duplicates or altered versions.
VisualData - Instagram for Visual Datasets
RevIMG - RevIMG is a reverse visual search engine.
NooBox - NooBox is a Chrome Extension that provides useful functions, such as: Multi-engine Reverse image search, Extract Images, Screenshot & Search
Bing Image Search - Now w/ related searches, Pinterest boards, and where to buy
Google - Google Search, also referred to as Google Web Search or simply Google, is a web search engine developed by Google. It is the most used search engine on the World Wide Web