I accidentally deleted my web browser history not realizing that I needed to revisit a confirmation page I received. Is there a way to restore my deleted safari history?

No.

First, from the Safari menu bar, select

Safari ▹ Preferences... ▹ Remove history items: Manually

Triple-click anywhere in the line below on this page to select it, then copy it to the Clipboard by pressing the key combination command-C:

~/Library/Safari

Quit Safari.

Select

Go ▹ Go to Folder

from the Finder menu bar. Paste into the text box that opens by pressing command-V, then press return.

A folder window should open. Inside that folder, there should be a file named

History.db (OS X 10.10 or later)

or

History.plist (OS X 10.9.5 or earlier)

Move that file to the Desktop.

Restore the file with that name from a backup that predates the changes. If you back up with Time Machine, enter it and scroll back to a snapshot of the open folder.

When you relaunch Safari, the old history should appear. When you're done with it, you can revert the change by replacing the history file with the one you moved to the Desktop. Otherwise, delete that file.

Revert the change in Safari's preferences to whatever you want it to be. If you leave it on Manually, the history file will grow without limit and may eventually slow down the browser.

I have a similar problem. Deleted Safari history on my iPhone which also deleted safari history on my Mac (iCloud I guess?)

Preparing for your suggested procedure I found that the file "~/Library/Safari/History.db" was created on April 11 and is quite large. So I did a quick check with the cat command in Terminal and saw that it has much more entries than I am shown in Safaris history menu.

So, maybe there is a way to convince Safari to show me the rest without involving time machine? Or any program to show "History.db" in a humanly readable way?

Uh, forget it 🙂 Opened the History.db with an Sqlite browser: despite size and age it seems only to contain what I can see in Safari. Off to time machine it is then …