Before installing
Check three things. First: that you downloaded the certificate on the same computer, browser and system user with which you made the request, because otherwise the FNMT process fails and you never get a file. Second: that you have the file's password, if you are installing from an exported copy. Third: that the certificate has not expired, which you can see in the file itself.
Where it ends up installed
On Windows the certificate is kept in the system store and is used by both Edge and Chrome. Firefox keeps its own store, so if you work with Firefox you must also import it there, from its certificate settings. On macOS it sits in Keychain Access and is used by Safari and Chrome.
That is the usual cause of the complaint «it works in one browser and not in another».
If the electronic office does not detect it
- Check that the certificate appears in the certificate manager and has not expired.
- Try another browser: if it works in one and not another, it is a matter of different stores, not of the certificate.
- Close and reopen the browser completely after importing.
- If the office asks you to sign and not just identify yourself, you also need the signing application. It is in the official electronic signature portal.
- Make a backup before touching anything else: exporting the certificate.
The five mistakes that make installation fail
Downloading on a different computer from the one that made the request. The FNMT ties the request code to the key pair generated in that browser. Changing computer, browser or even user profile invalidates the process and you start from zero, in-person identity check included.
Wiping the browser between request and download. Clearing data, resetting the browser or using incognito mode destroys the private key. If a week passes between requesting and downloading, do not touch that browser.
Forgetting that Firefox has its own store. Installing on Windows makes the certificate available to Edge and Chrome, but Firefox does not see it. It must be imported separately from its privacy and security settings.
Installing only the public part. If the private key was not ticked when exporting, the resulting file identifies but does not sign. You can tell because the system imports it without asking for a password.
Losing the export password. Nobody stores it and it cannot be recovered. Without it the .pfx file is a brick.
Checking it is properly installed
Installed is not the same as working. The check we always run before calling a certificate good is to actually enter an electronic office and sign something: downloading the employment history report is perfect, because it requires real identification and returns a PDF in seconds.
If the office does not offer the certificate in the list, check in this order: the certificate is in the right store for that browser, it has not expired, and AutoFirma is installed and up to date where the office requires it. On macOS also check in Keychain Access that the certificate appears with its private key attached, not on its own.
The electronic office does not recognise your certificate?
We leave it installed and tested on your computer and your phone, and check it works in the offices you will use.
Frequently asked questions
Can I install it on two computers?
Yes, by exporting it with its private key and importing it on the second computer.
Does it work in Firefox?
Yes, but Firefox uses its own certificate store: you must import it there too, the system one is not enough.
Do I need to be an administrator of the computer?
To install it in your user profile, normally not. For the machine store, yes.
What if I lost the file's password?
There is no way to recover it. You would have to obtain the certificate again from the beginning.
Legal basis
- Law 6/2020 regulating certain aspects of electronic trust services
- Law 39/2015 on Common Administrative Procedure, art. 14 on electronic dealings with the administration
- Royal Decree 203/2021, Regulation on public sector action by electronic means
Official sources
- FNMT: individual certificate
- FNMT: renewing the certificate
- Spanish Government electronic signature portal: downloads
- Importass, portal of the Social Security Treasury
Written by Irina Klein. Reviewed by Elena Alonso Volostnova, registered gestora administrativa (ICGA Valencia). Updated on 5 October 2026. This page is general information and does not replace personalised advice on your case.