The Oxford Learner's Dictionaries are an excellent resource. https://www.oxfordlearnersdictionaries.com/definition/english/internet Internet - noun BrE /ˈɪntənet/ ; NAmE /ˈɪntərnet/ (usually the Internet) (also informal the Net) [singular] an international computer network connecting other networks and computers from companies, universities, etc. I looked it up on the Internet. You can buy our goods over the Internet.

to Hiroshi Bowman: now i see the difference, thanks a lot!

To build upon Chris' answer, I would use "on the Internet" to refer to something done using the network known as the Internet. I would use "on Internet ___________" as a modifier, such as "on Internet devices" or "on Internet connections." In newspapers and other media, "internet" (without the capital "I") is becoming more common, more so in the UK but also in the US.

The Oxford Learner's Dictionaries are an excellent resource. https://www.oxfordlearnersdictionaries.com/definition/english/internet Internet - noun BrE /ˈɪntənet/ ; NAmE /ˈɪntərnet/ (usually the Internet) (also informal the Net) [singular] an international computer network connecting other networks and computers from companies, universities, etc. I looked it up on the Internet. You can buy our goods over the Internet.