The environment consists of data that is expected to be characteristic for performance and other behavior and not expected to change too often.

Changes to most of these data points are detected (where possible and sensible) and will lead to a session split in the “main” ping. The environment data may also be submitted by other ping types.

Note: This is not submitted with all ping types due to privacy concerns. This and other data is inspected under the data collection policy.

Some parts of the environment must be fetched asynchronously at startup. We don’t want other Telemetry components to block on waiting for the environment, so some items may be missing from it until the async fetching finished. This currently affects the following sections:

  • profile

  • add-ons

  • services


  build: {
    applicationId: <string>, // nsIXULAppInfo.ID
    applicationName: <string>, // "Firefox"
    architecture: <string>, // e.g. "x86", build architecture for the active build
    buildId: <string>, // e.g. "20141126041045"
    version: <string>, // e.g. "35.0"
    vendor: <string>, // e.g. "Mozilla"
    displayVersion: <string>, // e.g. "35.0b1"
    platformVersion: <string>, // e.g. "35.0"
    xpcomAbi: <string>, // e.g. "x86-msvc"
    updaterAvailable: <bool>, // Whether the app was built with app update available (MOZ_UPDATER)
  settings: {
    addonCompatibilityCheckEnabled: <bool>, // Whether application compatibility is respected for add-ons
    blocklistEnabled: <bool>, // true on failure
    isDefaultBrowser: <bool>, // null on failure and until session restore completes, not available on Android
    defaultSearchEngine: <string>, // e.g. "yahoo"
    defaultSearchEngineData: {, // data about the current default engine
      name: <string>, // engine name, e.g. "Yahoo"; or "NONE" if no default
      loadPath: <string>, // where the engine line is located; missing if no default
      origin: <string>, // 'default', 'verified', 'unverified', or 'invalid'; based on the presence and validity of the engine's loadPath verification hash.
      submissionURL: <string> // set for default engines or well known search domains
    defaultPrivateSearchEngine: <string>, // e.g. "duckduckgo"
    defaultPrivateSearchEngine: {,
      // data about the current default engine for private browsing mode. Same as defaultSearchEngineData.
    launcherProcessState: <integer>, // optional, values correspond to values of mozilla::LauncherRegistryInfo::EnabledState enum
    e10sEnabled: <bool>, // whether e10s is on, i.e. browser tabs open by default in a different process
    e10sMultiProcesses: <integer>, // Maximum number of processes that will be launched for regular web content
    fissionEnabled: <bool>, // whether fission is enabled this session, and subframes can load in a different process
    telemetryEnabled: <bool>, // false on failure
    locale: <string>, // e.g. "it", null on failure
    intl: {
      requestedLocales: [ <string>, ... ], // The locales that are being requested.
      availableLocales: [ <string>, ... ], // The locales that are available for use.
      appLocales: [ <string>, ... ], // The negotiated locales that are being used.
      systemLocales: [ <string>, ... ], // The locales for the OS.
      regionalPrefsLocales: [ <string>, ... ], // The regional preferences for the OS.
      acceptLanguages: [ <string>, ... ], // The languages for the Accept-Languages header.
    update: {
      channel: <string>, // e.g. "release", null on failure
      enabled: <bool>, // true on failure
      autoDownload: <bool>, // true on failure
    userPrefs: {
      // Only prefs which are changed are listed in this block
      "pref.name.value": value // some prefs send the value
      "pref.name.url": "<user-set>" // For some privacy-sensitive prefs
        // only the fact that the value has been changed is recorded
    attribution: { // optional, only present if the installation has attribution data
      // all of these values are optional.
      source: <string>, // referring partner domain, when install happens via a known partner
      medium: <string>, // category of the source, such as "organic" for a search engine
      campaign: <string>, // identifier of the particular campaign that led to the download of the product
      content: <string>, // identifier to indicate the particular link within a campaign
      variation: <string>, // name/id of the variation cohort used in the enrolled funnel experiment
      experiment: <string>, // name/id of the enrolled funnel experiment
      ua: <string>, // identifier derived from the user agent downloading the installer, e.g., chrome, Google Chrome 123
    sandbox: {
      effectiveContentProcessLevel: <integer>,
  // Optional, missing if fetching the information failed or had not yet completed.
  services: {
    // True if the user has a firefox account
    accountEnabled: <bool>,
    // True if the user has sync enabled.
    syncEnabled: <bool>
  profile: {
    creationDate: <integer>, // integer days since UNIX epoch, e.g. 16446
    resetDate: <integer>, // integer days since UNIX epoch, e.g. 16446 - optional
    firstUseDate: <integer>, // integer days since UNIX epoch, e.g. 16446 - optional
    wasCanary: <bool>, // Android only: true if this profile previously had a canary client ID
  partner: { // This section may not be immediately available on startup
    distributionId: <string>, // pref "distribution.id", null on failure
    distributionVersion: <string>, // pref "distribution.version", null on failure
    partnerId: <string>, // pref mozilla.partner.id, null on failure
    distributor: <string>, // pref app.distributor, null on failure
    distributorChannel: <string>, // pref app.distributor.channel, null on failure
    partnerNames: [
      // list from prefs app.partner.<name>=<name>
  system: {
    memoryMB: <number>,
    virtualMaxMB: <number>, // windows-only
    isWow64: <bool>, // windows-only
    isWowARM64: <bool>, // windows-only
    cpu: {
        count: <number>,  // desktop only, e.g. 8, or null on failure - logical cpus
        cores: <number>, // desktop only, e.g., 4, or null on failure - physical cores
        vendor: <string>, // desktop only, e.g. "GenuineIntel", or null on failure
        family: <number>, // desktop only, null on failure
        model: <number, // desktop only, null on failure
        stepping: <number>, // desktop only, null on failure
        l2cacheKB: <number>, // L2 cache size in KB, only on windows & mac
        l3cacheKB: <number>, // desktop only, L3 cache size in KB
        speedMHz: <number>, // desktop only, cpu clock speed in MHz
        extensions: [
          // as applicable:
          // "hasMMX", "hasSSE", "hasSSE2", "hasSSE3", "hasSSSE3",
          // "hasSSE4A", "hasSSE4_1", "hasSSE4_2", "hasAVX", "hasAVX2",
          // "hasAES", "hasEDSP", "hasARMv6", "hasARMv7", "hasNEON"
    device: { // This section is only available on mobile devices.
      model: <string>, // the "device" from FHR, null on failure
      manufacturer: <string>, // null on failure
      hardware: <string>, // null on failure
      isTablet: <bool>, // null on failure
    os: {
        name: <string>, // "Windows_NT" or null on failure
        version: <string>, // e.g. "6.1", null on failure
        kernelVersion: <string>, // android only or null on failure
        servicePackMajor: <number>, // windows only or null on failure
        servicePackMinor: <number>, // windows only or null on failure
        windowsBuildNumber: <number>, // windows only or null on failure
        windowsUBR: <number>, // windows 10 only or null on failure
        installYear: <number>, // windows only or null on failure
        locale: <string>, // "en" or null on failure
        hasPrefetch: <bool>, // windows only, or null on failure
        hasSuperfetch: <bool>, // windows only, or nul on failure
    hdd: {
      profile: { // hdd where the profile folder is located
          model: <string>, // windows only or null on failure
          revision: <string>, // windows only or null on failure
          type: <string>, // "SSD" or "HDD" windows only or null on failure
      binary:  { // hdd where the application binary is located
          model: <string>, // windows only or null on failure
          revision: <string>, // windows only or null on failure
          type: <string>, // "SSD" or "HDD" windows only or null on failure
      system:  { // hdd where the system files are located
          model: <string>, // windows only or null on failure
          revision: <string>, // windows only or null on failure
          type: <string>, // "SSD" or "HDD" windows only or null on failure
    gfx: {
        D2DEnabled: <bool>, // null on failure
        DWriteEnabled: <bool>, // null on failure
        ContentBackend: <string> // One of "Cairo", "Skia", or "Direct2D 1.1"
        Headless: <bool>, // null on failure
        //DWriteVersion: <string>, // temporarily removed, pending bug 1154500
        adapters: [
            description: <string>, // e.g. "Intel(R) HD Graphics 4600", null on failure
            vendorID: <string>, // null on failure
            deviceID: <string>, // null on failure
            subsysID: <string>, // null on failure
            RAM: <number>, // in MB, null on failure
            driver: <string>, // null on failure
            driverVendor: <string>, // null on failure
            driverVersion: <string>, // null on failure
            driverDate: <string>, // null on failure
            GPUActive: <bool>, // currently always true for the first adapter
        // Note: currently only added on Desktop. On Linux, only a single
        // monitor is returned for the primary screen.
        monitors: [
            screenWidth: <number>,  // screen width in pixels
            screenHeight: <number>, // screen height in pixels
            refreshRate: <number>,  // refresh rate in hertz (present on Windows only).
                                    //  (values <= 1 indicate an unknown value)
            pseudoDisplay: <bool>,  // networked screen (present on Windows only)
            scale: <number>,        // backing scale factor (present on Mac only)
        features: {
          compositor: <string>,     // Layers backend for compositing (e.g. "d3d11", "none", "opengl", "webrender")

          // Each the following features can have one of the following statuses:
          //   "unused"      - This feature has not been requested.
          //   "unavailable" - Safe Mode or OS restriction prevents use.
          //   "blocked"     - Blocked due to an internal condition such as safe mode.
          //   "blacklisted" - Blocked due to a blacklist restriction.
          //   "denied"      - Blocked due to allowlist restrictions.
          //   "disabled"    - User explicitly disabled this default feature.
          //   "failed"      - This feature was attempted but failed to initialize.
          //   "available"   - User has this feature available.
          // The status can also include a ":" followed by a reason
          // e.g. "FEATURE_FAILURE_WEBRENDER_VIDEO_CRASH_INTEL_23.20.16.4973"
          d3d11: { // This feature is Windows-only.
            status: <string>,
            warp: <bool>,           // Software rendering (WARP) mode was chosen.
            textureSharing: <bool>  // Whether or not texture sharing works.
            version: <number>,      // The D3D11 device feature level.
            blacklisted: <bool>,    // Whether D3D11 is blacklisted; use to see whether WARP
                                    // was blacklist induced or driver-failure induced.
          d2d: { // This feature is Windows-only.
            status: <string>,
            version: <string>,      // Either "1.0" or "1.1".
          gpuProcess: { // Out-of-process compositing ("GPU process") feature
            status: <string>, // "Available" means currently in use
          advancedLayers: { // Advanced Layers compositing. Only present if D3D11 enabled.
            status: <string>,    // See the status codes above.
          hwCompositing: { // hardware acceleration. i.e. whether we try using the GPU
            status: <string>
          wrCompositor: { // native OS compositor (CA, DComp, etc.)
            status: <string>
          wrSoftware: { // Software backend for WebRender, only computed when 'compositor' is 'webrender'
            status: <string>
          openglCompositing: { // OpenGL compositing.
            status: <string>
    appleModelId: <string>, // Mac only or null on failure
    sec: { // This feature is Windows 8+ only
      antivirus: [ <string>, ... ],    // null if unavailable on platform: Product name(s) of registered antivirus programs
      antispyware: [ <string>, ... ],  // null if unavailable on platform: Product name(s) of registered antispyware programs
      firewall: [ <string>, ... ],     // null if unavailable on platform: Product name(s) of registered firewall programs
  addons: {
    activeAddons: { // the currently enabled add-ons
      <addon id>: {
        blocklisted: <bool>,
        description: <string>, // null if not available
        name: <string>,
        userDisabled: <bool>,
        appDisabled: <bool>,
        version: <string>,
        scope: <integer>,
        type: <string>, // "extension", "service", ...
        foreignInstall: <bool>,
        hasBinaryComponents: <bool>,
        installDay: <number>, // days since UNIX epoch, 0 on failure
        updateDay: <number>, // days since UNIX epoch, 0 on failure
        signedState: <integer>, // whether the add-on is signed by AMO, only present for extensions
        isSystem: <bool>, // true if this is a System Add-on
        isWebExtension: <bool>, // true if this is a WebExtension
        multiprocessCompatible: <bool>, // true if this add-on does *not* require e10s shims
    theme: { // the active theme
      id: <string>,
      blocklisted: <bool>,
      description: <string>,
      name: <string>,
      userDisabled: <bool>,
      appDisabled: <bool>,
      version: <string>,
      scope: <integer>,
      foreignInstall: <bool>,
      hasBinaryComponents: <bool>
      installDay: <number>, // days since UNIX epoch, 0 on failure
      updateDay: <number>, // days since UNIX epoch, 0 on failure
    activePlugins: [
        name: <string>,
        version: <string>,
        description: <string>,
        blocklisted: <bool>,
        disabled: <bool>,
        clicktoplay: <bool>,
        mimeTypes: [<string>, ...],
        updateDay: <number>, // days since UNIX epoch, 0 on failure
    activeGMPlugins: {
        <gmp id>: {
            version: <string>,
            userDisabled: <bool>,
            applyBackgroundUpdates: <integer>,
  experiments: {
    "<experiment id>": { branch: "<branch>", type: "<type>", enrollmentId: "<id>" },
    // ...



Firefox builds downloaded from mozilla.org use a 14-digit buildId. Builds included in other distributions may have a different format (e.g. only 10 digits).



Note: Deprecated, use defaultSearchEngineData instead.

Contains the string identifier or name of the default search engine provider. This will not be present in environment data collected before the Search Service initialization.

The special value NONE could occur if there is no default search engine.

The special value UNDEFINED could occur if a default search engine exists but its identifier could not be determined.

This field’s contents are Services.search.defaultEngine.identifier (if defined) or "other-" + Services.search.defaultEngine.name if not. In other words, search engines without an .identifier are prefixed with other-.


Contains data identifying the engine currently set as the default.

The object contains:

  • a name property with the name of the engine, or NONE if no engine is currently set as the default.

  • a loadPath property: an anonymized path of the engine xml file, e.g. jar:[app]/omni.ja!browser/engine.xml (where ‘browser’ is the name of the chrome package, not a folder) [profile]/searchplugins/engine.xml [distribution]/searchplugins/common/engine.xml [other]/engine.xml [other]/addEngineWithDetails [other]/addEngineWithDetails:extensionID [http/https]example.com/engine-name.xml [http/https]example.com/engine-name.xml:extensionID

  • an origin property: the value will be default for engines that are built-in or from distribution partners, verified for user-installed engines with valid verification hashes, unverified for non-default engines without verification hash, and invalid for engines with broken verification hashes.

  • a submissionURL property with the HTTP url we would use to search. For privacy, we don’t record this for user-installed engines.

loadPath and submissionURL are not present if name is NONE.


This contains the data identifying the engine current set as the default for private browsing mode. This may be the same engine as set for normal browsing mode.

This object contains the same information as defaultSearchEngineData. It is only reported if the browser.search.separatePrivateDefault preference is set to true.


This object contains user preferences.

Each key in the object is the name of a preference. A key’s value depends on the policy with which the preference was collected. There are three such policies, “value”, “state”, and “default value”. For preferences collected under the “value” policy, the value will be the preference’s value. For preferences collected under the “state” policy, the value will be an opaque marker signifying only that the preference has a user value. The “state” policy is therefore used when user privacy is a concern. For preferences collected under the “default value” policy, the value will be the preference’s default value, if the preference exists. If the preference does not exist, there is no key or value.

The following is a partial list of collected preferences.

  • browser.search.suggest.enabled: The “master switch” for search suggestions everywhere in Firefox (search bar, urlbar, etc.). Defaults to true.

  • browser.urlbar.suggest.searches: True if search suggestions are enabled in the urlbar. Defaults to false.

  • browser.zoom.full (deprecated): True if zoom is enabled for both text and images, that is if “Zoom Text Only” is not enabled. Defaults to true. This preference was collected in Firefox 50 to 52 (Bug 979323).

  • security.tls.version.enable-deprecated: True if deprecated versions of TLS (1.0 and 1.1) have been enabled by the user. Defaults to false.

  • toolkit.telemetry.pioneerId: The state of the Pioneer ID. If set, then user is enrolled in Pioneer. Note that this does not collect the value.


This object contains the attribution data for the product installation.

Attribution data is used to link installations of Firefox with the source that the user arrived at the Firefox download page from. It would indicate, for instance, when a user executed a web search for Firefox and arrived at the download page from there, directly navigated to the site, clicked on a link from a particular social media campaign, etc.

The attribution data is included in some versions of the default Firefox installer for Windows (the “stub” installer) and stored as part of the installation. All platforms other than Windows and also Windows installations that did not use the stub installer do not have this data and will not include the attribution object.


This object contains data about the state of Firefox’s sandbox.

Specific keys are:

  • effectiveContentProcessLevel: The meanings of the values are OS dependent. Details of the meanings can be found in the Firefox prefs file. The value here is the effective value, not the raw value, some platforms enforce a minimum sandbox level. If there is an error calculating this, it will be null.



The assumed creation date of this client’s profile. It’s read from a file-stored timestamp from the client’s profile directory.


If the timestamp file does not exist all files in the profile directory are scanned. The oldest creation or modification date of the scanned files is then taken to be the profile creation date. This has been shown to sometimes be inaccurate (bug 1449739).


The time of the last reset time for the profile. If the profile has never been reset this field will not be present. It’s read from a file-stored timestamp from the client’s profile directory.


The time of the first use of profile. If this is an old profile where we can’t determine this this field will not be present. It’s read from a file-stored timestamp from the client’s profile directory.


Android-only. This attribute is set to true if the client ID was erroneously set to a canary client ID before and later reset to a new random client ID. The attribute is not included if the client ID was not changed.


If the user is using a partner repack, this contains information identifying the repack being used, otherwise “partnerNames” will be an empty array and other entries will be null. The information may be missing when the profile just becomes available. In Firefox for desktop, the information along with other customizations defined in distribution.ini are processed later in the startup phase, and will be fully applied when “distribution-customization-complete” notification is sent.

Distributions are most reliably identified by the distributionId field. Partner information can be found in the partner repacks (the old one is deprecated): it contains one private repository per partner. Important values for distributionId include:

  • “MozillaOnline” for the Mozilla China repack.

  • “canonical”, for the Ubuntu Firefox repack.

  • “yandex”, for the Firefox Build by Yandex.



This object contains operating system information.

  • name: the name of the OS.

  • version: a string representing the OS version.

  • kernelVersion: an Android only string representing the kernel version.

  • servicePackMajor: the Windows only major version number for the installed service pack.

  • servicePackMinor: the Windows only minor version number for the installed service pack.

  • windowsBuildNumber: the Windows build number.

  • windowsUBR: the Windows UBR number, only available for Windows >= 10. This value is incremented by Windows cumulative updates patches.

  • installYear: the Windows only integer representing the year the OS was installed.

  • locale: the string representing the OS locale.

  • hasPrefetch: the Windows-only boolean representing whether or not the OS-based prefetch application start-up optimization is set to use the default settings.

  • hasSuperfetch: the Windows-only boolean representing whether or not the OS-based superfetch application start-up optimization service is running and using the default settings.



Starting from Firefox 44, the length of the following string fields: name, description and version is limited to 100 characters. The same limitation applies to the same fields in theme and activePlugins.

Some of the fields in the record for each add-on are not available during startup. The fields that will always be present are id, version, type, updateDate, scope, isSystem, isWebExtension, and multiprocessCompatible. All the other fields documented above become present shortly after the sessionstore-windows-restored observer topic is notified.


Just like activeAddons, up-to-date information is not available immediately during startup. The field will be populated with dummy information until the blocklist is loaded. At the latest, this will happen just after the sessionstore-windows-restored observer topic is notified.


Just like activePlugins, this will report dummy values until the blocklist is loaded.


For each experiment we collect the

  • id (Like hotfix-reset-xpi-verification-timestamp-1548973, max length 100 characters)

  • branch (Like control, max length 100 characters)

  • type (Optional. Like normandy-exp, max length 20 characters)

  • enrollmentId (Optional. Like 5bae2134-e121-46c2-aa00-232f3f5855c5, max length 40 characters)

In the event any of these fields are truncated, a warning is printed to the console.

Version History

  • Firefox 70:

    • Added experiments.<experiment id>.enrollmentId. (bug 1555172)

  • Firefox 67:

    • Removed persona. The addons.activeAddons list should be used instead. (bug 1525511)

  • Firefox 61: