The Greek Small Letter Upsilon symbol (Ο ). Copy and paste it, or use its Unicode, HTML, and CSS codes.
More from Greek Letters.
The quickest way is to copy Ο from this page and paste it anywhere. You can also insert it with its Unicode, HTML, or alt code listed above.
Ο is U+03C5 (decimal 965).
Use υ in HTML to render Ο on a web page.
On Windows you can type it with Alt+965 (hold Alt and enter the number on the numeric keypad).
Yes β copying is completely free and unlimited, and works right in your browser with no sign-up.