This document describes Preferences affecting the Firefox’s address bar. Preferences that are generated and updated by code won’t be described here.

User Exposed

These preferences are exposed through the Firefox UI.

browser.urlbar.shortcuts.bookmarks (boolean, default: true)

Whether to show the bookmark search shortcut button in the view. Can be controlled from Search Preferences.

browser.urlbar.shortcuts.tabs (boolean, default: true)

Whether to show the tabs search shortcut button in the view. Can be controlled from Search Preferences.

browser.urlbar.shortcuts.history (boolean, default: true)

Whether to show the history search shortcut button in the view. Can be controlled from Search Preferences.

browser.urlbar.showSearchSuggestionsFirst (boolean, default: true)

Whether to show search suggestions before general results. Can be controlled from Search Preferences.

browser.urlbar.showSearchTerms.enabled (boolean, default: true)

Whether to show the search term in the urlbar on a default search engine results page. Can be controlled from Search Preferences.

browser.urlbar.suggest.bookmark (boolean, default: true)

Whether results will include the user’s bookmarks. Can be controlled from Privacy Preferences.

browser.urlbar.suggest.history (boolean, default: true)

Whether results will include the user’s history. Can be controlled from Privacy Preferences.

browser.urlbar.suggest.openpage (boolean, default: true)

Whether results will include switch-to-tab results. Can be controlled from Privacy Preferences.

browser.urlbar.suggest.searches (boolean, default: true)

Whether results will include search suggestions. Can be controlled from Search Preferences.

browser.urlbar.suggest.engines (boolean, default: true)

Whether results will include search engines (e.g. tab-to-search). Can be controlled from Privacy Preferences.

browser.urlbar.suggest.topsites (boolean, default: true)

Whether results will include top sites and the view will open on focus. Can be controlled from Privacy Preferences. (boolean, default: true)

Whether search suggestions are enabled globally, including the separate search bar. Can be controlled from Search Preferences. (boolean, default: false)

When search suggestions are enabled, controls whether they are provided in Private Browsing windows. Can be controlled from Search Preferences.


These preferences are normally hidden, and should not be used unless you really know what you are doing.

browser.urlbar.accessibility.tabToSearch.announceResults (boolean: default: true)

Whether we announce to screen readers when tab-to-search results are inserted.

browser.urlbar.autoFill (boolean, default: true)

Autofill is the the feature that automatically completes domains and URLs that the user has visited as the user is typing them in the urlbar textbox.

browser.urlbar.autoFill.adaptiveHistory.enabled (boolean, default: false)

Whether adaptive history autofill feature is enabled.

browser.urlbar.autoFill.adaptiveHistory.useCountThreshold (float, default: 1.0)

Threshold for use count of input history that we handle as adaptive history autofill. If the use count is this value or more, it will be a candidate.

browser.urlbar.bestMatch.enabled (boolean, default: false)

Whether the best match feature is enabled.

browser.urlbar.autoFill.stddevMultiplier (float, default: 0.0)

Affects the frecency threshold of the autofill algorithm. The threshold is the mean of all origin frecencies, plus one standard deviation multiplied by this value.

browser.urlbar.ctrlCanonizesURLs (boolean, default: true)

Whether using ctrl when hitting return/enter in the URL bar (or clicking ‘go’) should prefix ‘www.’ and suffix browser.fixup.alternate.suffix to the user value prior to navigating.

browser.urlbar.decodeURLsOnCopy (boolean, default: false)

Whether copying the entire URL from the location bar will put a human readable (percent-decoded) URL on the clipboard.

browser.urlbar.delay (number, default: 50)

The amount of time (ms) to wait after the user has stopped typing before fetching certain results. Reducing this doesn’t make the Address Bar faster, it will instead make it access the disk more heavily, and potentially make it slower. Certain results, like the heuristic, always skip this timer anyway.

browser.urlbar.dnsResolveSingleWordsAfterSearch (number, default: 0)

Controls when to DNS resolve single word search strings, after they were searched for. If the string is resolved as a valid host, show a “Did you mean to go to ‘host’” prompt. Set to 0. 0: Never resolve, 1: Use heuristics, 2. Always resolve.

browser.urlbar.eventTelemetry.enabled (boolean, default: false)

Whether telemetry events should be recorded. This is expensive and should only be enabled by experiments with a small population.

browser.urlbar.extension.timeout (integer, default: 400)

When sending events to extensions, they have this amount of time in milliseconds to respond before timing out. This affects the omnibox API.

browser.urlbar.filter.javascript (boolean, default: true)

When true, javascript: URLs are not included in search results for safety reasons.

browser.urlbar.formatting.enabled (boolean, default: true)

Applies URL highlighting and other styling to the text in the urlbar input field. This should usually be enabled for security reasons.

browser.urlbar.maxCharsForSearchSuggestions (integer, default: 100)

As a user privacy measure, we don’t fetch results from remote services for searches that start by pasting a string longer than this. The pref name indicates search suggestions, but this is used for all remote results.

browser.urlbar.maxHistoricalSearchSuggestions (integer, default: 2)

The maximum number of form history results to include as search history.

browser.urlbar.maxRichResults (integer, default: 10)

The maximum number of results in the urlbar popup.

browser.urlbar.merino.clientVariants (string, default: “”)

Comma separated list of client variants to send to send to Merino. See Merino API docs for more details. This is intended to be used by experiments, not directly set by users.

browser.urlbar.merino.enabled (boolean, default: false)

Whether Merino is enabled as a quick suggest source.

browser.urlbar.merino.providers (string, default: “”)

Comma-separated list of providers to request from the Merino server. Merino will return suggestions only for these providers. See Merino API docs for more details.

browser.urlbar.openintab (boolean, default: false)

Whether address bar results should be opened in new tabs by default.

browser.urlbar.quicksuggest.enabled (boolean, default: false)

Whether the quick suggest feature is enabled, i.e., sponsored and recommended results related to the user’s search string. This pref can be overridden by the quickSuggestEnabled Nimbus variable. If false, neither sponsored nor non-sponsored quick suggest results will be shown. If true, then we look at the individual prefs browser.urlbar.suggest.quicksuggest.nonsponsored and browser.urlbar.suggest.quicksuggest.sponsored.

browser.urlbar.quicksuggest.remoteSettings.enabled (boolean, default: true)

Whether remote settings is enabled as a quick suggest source.

browser.urlbar.quicksuggest.dataCollection.enabled (boolean, default: false)

Whether data collection is enabled for quick suggest results.

browser.urlbar.quicksuggest.shouldShowOnboardingDialog (boolean, default: true)

Whether to show the quick suggest onboarding dialog.

browser.urlbar.richSuggestions.tail (boolean, default: true)

If true, we show tail search suggestions when available.

browser.urlbar.searchTips.test.ignoreShowLimits (boolean, default: false)

Disables checks that prevent search tips being shown, thus showing them every time the newtab page or the default search engine homepage is opened. This is useful for testing purposes.

browser.urlbar.speculativeConnect.enabled (boolean, default: true)

Speculative connections allow to resolve domains pre-emptively when the user is likely to pick a result from the Address Bar. This allows for faster navigation.

browser.urlbar.sponsoredTopSites (boolean, default: false)

Whether top sites may include sponsored ones.

browser.urlbar.suggest.bestmatch (boolean, default: true)

Whether to show the best match result is enabled. This pref is ignored if browser.urlbar.bestMatch.enabled is false.

browser.urlbar.suggest.quicksuggest.nonsponsored (boolean, default: false)

Whether results will include non-sponsored quick suggest suggestions.

browser.urlbar.suggest.quicksuggest.sponsored (boolean, default: false)

Whether results will include sponsored quick suggest suggestions.

browser.urlbar.switchTabs.adoptIntoActiveWindow (boolean, default: false)

When using switch to tabs, if set to true this will move the tab into the active window, instead of just switching to it.

browser.urlbar.trimURLs (boolean, default: true)

Clean-up URLs when showing them in the Address Bar.

keyword.enabled (boolean, default: true)

By default, when the search string is not recognized as a potential url, search for it with the default search engine. If set to false any string will be handled as a potential URL, even if it’s invalid.

browser.fixup.dns_first_for_single_words (boolean, default: false)

If true, any single word search string will be sent to the DNS server before deciding whether to search or visit it. This may add a delay to the urlbar.


These preferences are experimental and not officially supported. They could be removed at any time.

browser.urlbar.suggest.calculator (boolean, default: false)

Whether results will include a calculator.

browser.urlbar.unitConversion.enabled (boolean, default: false)

Whether unit conversion is enabled.

browser.urlbar.unitConversion.suggestedIndex (integer, default: 1)

The index where we show unit conversion results.

browser.urlbar.experimental.expandTextOnFocus (boolean, default: false)

Whether we expand the font size when the urlbar is focused.

browser.urlbar.experimental.searchButton (boolean, default: false)

Whether to displays a permanent search button before the urlbar.

browser.urlbar.keepPanelOpenDuringImeComposition (boolean, default: false)

Whether the results panel should be kept open during IME composition. The panel may overlap with the IME compositor panel.

browser.urlbar.restyleSearches (boolean, default: false)

When true, URLs in the user’s history that look like search result pages are restyled to look like search engine results instead of history results.

browser.urlbar.update2.emptySearchBehavior (integer, default: 0)

Controls the empty search behavior in Search Mode: 0. Show nothing, 1. Show search history, 2. Show search and browsing history


These preferences should not be used and may be removed at any time.

browser.urlbar.autoFill.searchEngines (boolean, default: false)

If true, the domains of the user’s installed search engines will be autofilled even if the user hasn’t actually visited them.

browser.urlbar.usepreloadedtopurls.enabled (boolean, default: false)

Results will include a built-in set of popular domains when this is true.

browser.urlbar.usepreloadedtopurls.expire_days (integer, default: 14)

After this many days from the profile creation date, the built-in set of popular domains will no longer be included in the results.