How to Enable IDN Punycode in Firefox Address Bar

Punycode is a special encoding used to convert Unicode characters to ASCII, which is a smaller, more restricted character set than Unicode. Punycode is used to encode internationalized domain names (IDNs) as a defense against address spoofing. Firefox allows enabling IDN punycode instead of non-Latin letters and Unicode symbols. This can be very useful, as you can find out if the currently opened web page is a phishing site or just a non-official mirror of some web site which you would like to avoid.


Take a look at this picture:

Binance PhishingBinance Ok

At first glance, the addresses look very similar. Some users may not pay attention to the small dots below the "n" letter, which are there because it is a unicode symbol 'n with a dot below it' (U+1E47). This way, phishing web sites may trick you and make you believe that you are visiting the official genuine site.

For advanced protection, you can enable IDN Punycode protection in Firefox. With the option enabled, the address becomes like this:

Binance With Punicode

Obviously, it doesn't look like the right web address any more.

If you find this feature useful and would like to enable it, here is how.

To enable IDN Punycode in Firefox Address Bar, do the following.

      1. Open a new tab and enter the following text in the address bar:

        Confirm that you will be careful if a warning message appears for you.Firefox 57 About Config Confirmation

      2. Enter the following text in the search box:

        See the following screenshot:Firefox Enable IDN Punycode

      3. You will see the parameter network.IDN_show_punycode. Double-click on it to set it to true.

You are done. This will enable IDN punycode in Firefox.

If some day you change your mind, open the about:config page again, find the network.IDN_show_punycode parameter and set it to false. This will disable the feature.

Are you a regular user of Mozilla Firefox? Recently, the browser underwent a significant change with the huge release of Firefox Quantum. The browser comes with a new user interface, codenamed "Photon", and features a new engine "Quantum". It was a difficult move for developers, because with this release, the browser drops support for XUL-based add-ons completely! All of the classic add-ons are deprecated and incompatible, and only a few have moved to the new WebExtensions API.

The Quantum engine is all about parallel page rendering and processing. It is built with a multi-process architecture for both CSS and HTML processing, which makes it more reliable and faster.

Unfortunately, IDN Punycode is not enabled by default in this browser, so it is a security risk from my point of view. Now you know what to do to enable it.

Source and image credits: Mattias Geniar


7 thoughts on “How to Enable IDN Punycode in Firefox Address Bar

  1. doubleagent

    This is a useful feature. Thanks.

    1. Sergey Tkachenko Post author

      You are welcome.

  2. Phil

    thank you for sharing information

    1. Sergey Tkachenko Post author

      you are most welcome Phil

  3. Alicia

    i love it!

  4. Xahid

    Thanks for sharing, its really useful to avoid phishing sites.
    I wonder if we update the Firefox to next up-coming version, will it overwrite with default values.

    1. Sergey Tkachenko Post author

      It should not


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