wget is basically to retrieve HTTP contents from web servers. I want to know if wget is based on TCP or UDP? I did a search but some resources said it is TCP while others said UDP.
GNU Wget is a free utility for non-interactive download of files from the Web. It supports HTTP, HTTPS, and FTP protocols, as well as retrieval through HTTP proxies.
HTTP, HTTPS, and FTP are all TCP protocols (and respectively use default TCP ports 80, 443, and 20/21). Therefore the answer to your question is: wget uses TCP.
Any source that could have said that wget uses UDP is plain wrong. Since UDP is a connectionless, unreliable, not-acknowledged protocol, it is unfit for file transfer.