As a KeePassXC user, this extension is absolute gold. Getting it to work isn't entirely intuitive. Tips from a happy user:

Make sure the KeePassXC database has permission to link by checking off the relevant boxes under Tools > Settings > Browser Integration and Database Settings > Browser Integration. Don't close KeePassXC. Go to the extension and connect it under Settings > Connected Databases. In order for this extension to function, KeePassXC *must be running*. In KeePassXC, you can choose to minimize or hide the program instead of quitting under Tools > Settings. In the KeePass entry itself, don't forget to specify a URL.

Like it! brings all my passwords together in one place, where I can control them.
TNX Guys for the extension.

No matter how many times I click on the add database button it will not work, rendering the Add-On useless

It's really a convenience to use this add-on with KeePassXC. But, there been an issue that has been raised several months back :

In my case
Firefox 83
KeePassXC-Browser 1.7.3
Ubuntu 20.04 LTS

`keepassxc-proxy` makes tcp connections to remote servers over internet & transfers data(with 36+ KB/s speed) without user permission under Linux root privileges.

tcp 0 0 192.168.42.245:52470 117.18.237.29:80 ESTABLISHED 20559/keepassxc-pro
tcp 0 392 192.168.42.245:34738 209.216.230.240:443 ESTABLISHED 20225/keepassxc-pro

tcp 1 0 192.168.42.245:49194 172.67.146.206:443 CLOSE_WAIT 20225/keepassxc-pro
tcp 1 0 192.168.42.245:53060 104.20.214.50:443 CLOSE_WAIT 20225/keepassxc-pro
tcp 1 0 192.168.42.245:60362 172.67.153.104:443 CLOSE_WAIT 20225/keepassxc-pro
tcp 25 0 192.168.42.245:39074 151.101.113.137:443 CLOSE_WAIT 20225/keepassxc-pro
tcp 7890 0 192.168.42.245:34738 209.216.230.240:443 CLOSE_WAIT 20225/keepassxc-pro

simple ip2location domain :
104.20.214.50 .... CloudFlare Inc.
117.18.237.29 .... edgecast.com
151.101.113.137 .. fastly.com
172.67.146.206 ... CloudFlare Inc.
172.67.153.104 ... CloudFlare Inc.
209.216.230.240 .. M5 Computer Security

I tried several times, had to lock password-DB out of fear.

This bug/issue is not addressed by Firefox, claim KeePassXC team on their issue-tracker-logs.

I'm in a limbo, is Firefox breaching user privacy without their knowledge; what data is being transferred to remote servers by keepassxc-proxy?
Should I abandon Firefox; isn't it the most secure (or configurable) browser out there?
Should I change passwords of hundreds of accounts now?

I'm using AutoTyping where ever it's possible & often wished they had auto-type separately for Username & Password; you know for pages like firefox or google account logins.

cheers

Me costó un poco conectarla al principio pero siguiendo la pista de la documentación lo logré en seguida. Una maravilla para la seguridad de nuestras contraseñas!

Requires an application installed to work.

Edit: It turns out the checkbox for Browser Integration with Firefox/Tor Browser became unchecked for some reason. After rechecking it, it works without a problem.

I've gotten KeepassXC set up on Brave and Vivaldi already. But this Firefox extension just gives me the error: "Key exchange was not successful" when I try to reload the connection.

Just doesn't work.
Behaviour is so random. Extension works for some sites, and completely fails for others (about 70% of the websites I browse).
The most frustrating thing, is that this green icon appears in the login field, but nothing happens when you press it.
To be noted, this is consistent whichever browser I use (FF or Chrome) and whichever OS I run (Windows 10 or Linux Mint).

I gave a KeepassXC and the browser extension a try because it looked promising, and the KeepassXC GUI is nicer to plain Keepass, but it seems I have no other option than revert to Keepass + RPC pluging + Kee browser extension.

Sad.

EDIT: see bottom for additional (positive) impressions and alternatives.

Original Review:

This is almost perfect, but KeePassXC-Browser is having problems with certain websites which require more than a UserID and Password field.

For example, on the American Airlines site, a username, *last name* and PW are required. While KeePassXC allows me to enter additional attributes like "Last Name: Doe" into advanced, there does not seem to be a way to invoke pasting it into the form.

Even If one uses the "choose custom login fields" there is no way to set the last name field as one of the options . . .

Ah, well. At least there is auto-type! :-)

EDIT: The developer is fantastically responsive, as seen below (and I was also e-mail directly with further comments, a nice touch!). I pointed out the built-in documentation (of KeePassXC) is missing the "KPH:" detail (required in KeePassXC-**Browser**) given in the response (but *is* shown in the online docs which I had not yet read).

Hopefully the built-in docs and online docs become better synchronized.

If you anyone still has problems with KeePassXC-Browser, it seems there are other Firefox add-ons which can connect to KeePassXC such as "KeePassHttp-Connector."

Also, standalone add-ons such as "Owl" (not yet reviewed, but much newer than...) or "KeePass Tusk" make the promise of not needing to install a connector to KeePassXC in the first place.

Would love to see this as a featured plugin. Great work being done here. Thanks for all the effort!