If you need browser extensions, try the Privacy Guides page.

Chromium flags

These can generally be found from about:flags on Chromium based browsers, for Vivaldi explicit vivaldi://flags is required and it also has chrome://settings for the usual Chromium settings.

  • #enable-quic - enabled
  • #enable-force-dark - enabled with increased text constract
  • #force-color-profile - sRGB
  • #trust-tokens - enabled


These likely also exist, but just without the vendor- part when searhcing.

  • #edge-automatic-https - enabled
  • #edge-autoplay-user-setting-block-option
  • #edge-tab-groups - enabled
  • #edge-tab-groups-auto-create - enabled
  • #edge-tab-groups-collapse-freezing - enabled

Firefox about:config

  • privacy.firstparty.isolate to true for preventing domains from accessing each other’s data.
  • browser.newtabpage.activity-stream.showSponsored & browser.newtabpage.activity-stream.showSponsored to false to stop sponsored links.
  • dom.security.https_only_mode to true to force HTTPS and not need HTTPS Everywhere
  • security.certerrors.mitm.auto_enable_enterprise_roots to false in order to not trust system CA store in case of enterprise MITM
  • security.OCSP.require to true in order to not allow OCSP soft fail. I am not sure if this is a good idea.
  • privacy.resistFingerprinting.letterboxing = true so letterboxing is used to hide real browser size. Tor Browser support
  • `extensions.pocket.enabled` to `false` so the Pocket integration goes away
  • On Linux widget.content.gtk-theme-override (a string that has to be created by user) to Adwaita:light so text boxes in dark themes become readable, thank you Dovydas Venckus
  • image.animation_mode to once in order to have gifs play once and then stop everywhere (none to never have them play).
  • geo.provider.network.url to https://location.services.mozilla.com/v1/geolocate?key=%MOZILLA_API_KEY% in order to send nearby WiFi networks to Mozilla instead of Google. See also MLS Software.
  • `media.peerconnection.enabled` to `false` in order to disable WebRTC (potential IP leaker, will break VoIP/calls, but those are better outside of Firefox anyway)

    Not needed anymore in 2020, WebRTC has improved to not do that.

    • media.navigator.enabled to false in order to also hide cameras and microphones from websites. I am not sure if this is still necessary either, but maybe it will remind me that I have focused my VoIP to Chromium?
  • network.IDN_show_punycode to true in order to see punycode instead of UTF-8 in case of spoofing attempt. However makes reading non-ASCII domains painful.
  • reader.parse-on-load.force-enabled to true in order to allow reader use to be used on ~all websites and devices (regardless of low RAM?)
  • toolkit.telemetry.server to empty in order to not send telemetry (which may be blocked by filtering DNS providers such as AdGuard or NextDNS resulting high amount of failing queries)

Future note: network.dns.blockDotOnion;false ?


  • network.trr.bootstrapAddress DNS server to use for resolving the DoH name, e.g. (Resolver 2 of Quad9)
  • network.trr.mode depends, 2 to prefer DoH, but fallback to system resolver (or 3 to enforce DoH without fallback). If there is system encrypted DNS, just take 5 to at least benefit from the system DNS cache.
    • DoH is required by Firefox ESNI support which encrypts SNI which would still leak which sites you visit. Another bug about ESNI + Android DoT
    • I have ended up to recommending 2 as otherwise the DoH server going down stops DNS from working on your Firefox entirely, which may be more of a problem than unencrypted SNI as not everyone supports it.
      • since then I have decided that 5 is the best option, because otherwise it goes past my Unbound setup. I hope Mozilla/Firefox will fix the two bugs linked above, so I don’t have to choose between DNS under my control vs encrypted SNI.
  • network.trr.early-AAAA true to hopefully prefer IPv6
  • network.trr.uri for the actual resolver address, e.g. https://dns.quad9.net/dns-query or (removes the need for network.trr.bootstrapAddress and allows network.trr.mode 3?) or Privacy Guides list of Encrypted DNS Resolvers

Some notes:

  • You can confirm TRR working by visiting about:networking#dns where you should be seeing DNS cache of Firefox and a lot of TRR: true.
  • Quad9 became my preferred resolver through anxiety about other options being small (and possibly more likely to go down) or commercial while Quad9 is non-profit organization and 2019-03-20 apparently the default fallback resolver of dnscrypt-proxy (at least in Debian).
  • Quad9 while having filtering of malicious domains should be easy to figure out as the problem if something doesn’t work on my computers as due to the previously mentioned bug I am mainly using it on Firefox.
  • While investingating how Android 9 Private DNS works, I also wrote a DNS provider comparsion here


This information is from Arch Wiki on Firefox tweaks

  • browser.cache.disk.enable to false to only cache to RAM.
  • (browser.cache.memory.enable to true which should be default)
  • browser.sessionstore.interval to 600000 in order to only store open session every ten minutes (instead of 15 seconds) in case of crashes.
    • alternatively browser.sessionstore.resume_from_crash to false to not store the session data for crash recovery at all. I think this may be the more healthy option with all the information flood and dozens of tabs.


Every object loaded (html page, jpeg image, css stylesheet, gif banner) is saved in the Firefox cache for future use without the need to download it again. It is estimated that only a fraction of these objects will be reused, usually about 30%. This because of very short object expiration time, updates or simply user behavior (loading new pages instead of returning to the ones already visited). The Firefox cache is divided into memory and disk cache and the latter results in frequent disk writes: newly loaded objects are written to memory and older objects are removed.

Firefox stores the current session status (opened urls, cookies, history and form data) to the disk on a regular basis. It is used to recover a previous session in case of crash. The default setting is to save the session every 15 seconds, resulting in frequent disk access.

and this is the reason why Firefox is at times accused of killing SSDs.

Changelog: GitHub.com commits gitea.blesmrt.net commits