How to Host your Unity Game Online

Create a WebGL Build
To how your Unity Game Online follow these steps:
File > Build Settings > Platform > WebGL > Switch Platform-button
(Checking Development Build allows for some special debugging)
For WebGL you’ll need to use Gamma color space:
Player settings > Player > Other Settings > Color Space
Click Build
Choose a file location > Wait > Build save location will pop up
You can take these 3 files and upload them if you have a web server.
To test you game locally in your browser open the index.html file.
Host Online
For example you can use SIMMER.io
Free hosting for WebGL Unity games which you can embed on your sites.
Sign up drag and drop and follow the instructions on the site.