If you use the password keeper app 1Password you can immediately open this app from within Safari by entering a command in the address field of Safari.
To improve the usability of entering the command first define a shortcut.
A shortcut on iOS devices are some letters or numbers which expand into a word or phrase as you type it.
Shortcuts are often used to expand some characters to the complete E-Mail address.
Define aid as a shortcut and email@example.com as the phrase. If you then type aid anywhere on your device it’s expanded to the E-Mail address.
Go to Settings – General – Keyboard – Shortcuts.
Tap on ‘+’ and enter
for the phrase and pp for the shortcut (or any other shortcut).
Open a website in Safari.
Go to the field which contains the website’s address. Tap on the Cross to remove the content and enter your shortcut pp and tap on Go.
1Password opens and displays the website with its own integrated browser.
In the app you can now define a new login for this website with its credentials.
Problems with shortcuts …
When typing a shortcut you have to tap on the space bar to expand it.
If you use a shortcut in an input field e.g. 1Password’s field ‘username’ within the ‘Login’ category the app transmits the entire content of this field to the website including the following space character (blank) added by using the space bar.
Apple’s website for example then informs you about wrong credentials due to the following blank. You can only see where the problem is if you mark the whole input field. The marker shows you the additional blank and you have to manually delete it.
This is definitely not user friendly as most of the usernames today are E-Mail addresses and shortcuts are used to automatically fill in these addresses.
1Password and some website developers should fix this like Microsoft did it many years ago with input fields in Microsoft Access forms. They stripped off all following blanks as it makes no sense to save them.