Opera
Use one of the following:
Hold the Ctrl key and press the F5 key.
Hold the ⇧ Shift key and press the F5 key.
Hold the Ctrl key and click the Reload button
on the navigation toolbar.
Hold the ⇧ Shift key and click the Reload button
on the navigation toolbar.
Internet Explorer
Use one of the following:
Hold the Ctrl key and press the F5 key.
Hold the Ctrl key and click the "Refresh" button on the toolbar.
Google Chrome
On Windows, use one of the following:
Hold the Ctrl key and press the F5 key.
Hold the ⇧ Shift key and press the F5 key.
Hold the Ctrl key and click the Reload button
on the navigation toolbar.
Hold the ⇧ Shift key and click the Reload button
on the navigation toolbar.
On Mac OS X:
Hold both the ⌘ Cmd and ⇧ Shift keys
and press the R key.
On Linux:
Hold the Ctrl key and press the F5 key.
Firefox and other related browsers
These instructions work for Firefox, SeaMonkey, and other related browsers.
On Windows and Linux, use one of the following:
Hold both the Ctrl and ⇧ Shift keys
and then press R.
Hold the ⇧ Shift key and click the Reload button
on the navigation toolbar.
Hold the Ctrl key and press the F5 key.
On Mac OS X, use one of the following:
Hold both the ⌘ Cmd and ⇧ Shift keys
and then press R.
Hold the ⇧ Shift key and click the Reload button
on the navigation toolbar.
Safari
For version 4 and newer:
Hold down the ⇧ Shift key and click the Reload toolbar button.
For version 3 and older:
Hold down the ⌘ Cmd key and press R.
This kind of "regular" reload will usually bypass the cache.
Note that Apple claims that clicking the "Reload" toolbar button has the same effect as ⌘ Cmd+R, but this is not true; frequently the button will not bypass the cache.
Konqueror
Press F5 or click the "Reload" button on the toolbar.
Bypassing cache
That's quite thorough. I'd suggest moving opera to the top due to the fact that the question asks how to do it in Opera only. – dudewad – 2017-09-03T23:01:13.897
In macOS opera it's now option-command-R – congusbongus – 2018-11-10T03:28:28.707