I'm building an app that needs to check bad websites and was wondering if there is a way to download the Firefox bad site list directly outside of the browser? The list is described in the Mozilla.org knowledgebase article below and is automatically downloaded by the Firefox browser every 30 minutes.

This question is specifically for the list that Firefox downloads, not the Google Safe Browsing service.

The Mozilla KB article says the following:

How does Phishing and Malware Protection work in Firefox?

Phishing and Malware Protection works by checking the sites that you visit against lists of reported phishing, unwanted software and malware sites. These lists are automatically downloaded and updated every 30 minutes or so when the Phishing and Malware Protection features are enabled.

When you download an application file, Firefox checks the site hosting it against a list of sites known to contain "malware". If the site is found on that list, Firefox blocks the file immediately, otherwise it asks Google’s Safe Browsing service if the software is safe by sending it some of the download’s metadata.

1 Answer 1


The phishing and malware protection in Firefox is provided with Google Safe Browsing service. This is not a list you can download.

It is instead a database with an SDK on top of it which provides an offline way to determine if a specific URL might be dangerous and which requires in the positive case an additional online verification to eliminate false positives. This additional check is necessary since the blacklisted URL's are not stored in plain but are hashed which might lead to collisions. This hashing is done so that the information can be stored in a memory efficient way and also so that the blacklist cannot be reversed. For more information see the API documentation.

I'm building an app that needs to check bad websites ...

Depending on your use case you can use the provided API for free or you have to use the commercial Web Risk API.

  • Good links. However, Firefox only uses Google Safe Browsing service if the website is not on the list that it does download every 30 minutes per the Firefox KB article: support.mozilla.org/en-US/kb/…
    – Grokify
    Commented Sep 25, 2019 at 4:30
  • @Grokify: The wording in the KB is misleading. The behavior they describe is exactly what is required when using the offline database for Google Safe Browsing: Firefox is using the Update API of Google Safe Browsing to update the database every 30 minutes. If a match is found it checks online if the match was a false positive or not. There is no other source Firefox is using for protection. Commented Sep 25, 2019 at 5:12

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