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Networking Preferences

Abstract:
List of preferences that affect networking behavior.
Description of acceptable values and behavior.

Audience:
QA testers, developers and "power users" with extensive networking internals experience.
For general technical documentation on preferences (including how to edit them), see "A Brief Guide to Mozilla Preferences"

Feedback:
and comments to bug 198252.

Overview:
The sections are in roughly alphabetical + functional order.
The preferences are in order of usage by the UI (which is not often alphabetical order).
Relevant bugs are provided only when absolutely necessary.

NOTE: Do not change any of these via about:config unless you know what you are doing. If you are uncertain what that phrase means, you probably do not.

If you qualify, you are probably one or more of the following:
  • You have a feature-spec or code-level understanding of the preference.
  • You are doing testing and have a clear performance metric.
  • You are doing this in conjunction with a packet trace to monitor Necko's changed behavior.

    HTTP (this section under construction)
    Preference Name Acceptable Values Preferences UI  (in bold) and comments
    general.useragent.contentlocale
    string

    general.useragent.misc
    (major version number) string

    general.useragent.security
    string

    network.http.accept-encoding
    gzip,deflate (default string)
    no UI
    network.http.accept.default text/xml,application/xml,
    application/xhtml+xml,text/html;

    q=0.9,text/plain;
    q=0.8,video/x-mng,image/png,
    image/jpeg,image/gif;

    q=0.2,*/*;q=0.1

    network.http.default-socket-type (empty) default
    ?
    network.http.keep-alive true (default)

    network.http.keep-alive.timeout 30
    no UI
    network.http.max-connections 24

    network.http.max-connections-per-server 8

    network.http.max-persistent-connections-per-proxy 4

    network.http.max-persistent-connections-per-server
    2

    network.http.pipelining false ? (on in mozilla, greyed)
    network.http.pipelining.firstrequest false

    network.http.pipelining.maxrequests
    4

    network.http.proxy.keep-alive true (default)

    network.http.proxy.pipelining false
    ? (on in mozilla, greyed)
    network.http.proxy.version 1.1 (default)
    1.0

    network.http.redirection-limit
    20

    network.http.request.max-start-delay
    10

    network.http.sendRefererHeader
    2

    network.http.sendSecureXSiteReferrer
    true

    network.http.use-cache
    true

    network.http.version
    1.1 (default)
    1.0



    File
    Preference Name Acceptable Values
    Preferences UI and comments
    security.checkloaduri true (default)
    false
    No UI
    checkloaduri will disable file:// URLs on pages
    from a network (http: https: ftp:) source, for security reasons.
    Errors are sent to the javascript console, not to the user via dialog box. This preference only works in Gecko versions before 1.8 (so Firefox 1.0 and Mozilla Suite builds). In Firefox 1.5 and Seamonkey 1.0 this preference no longer has an effect.

    FTP (see also Proxy)
    Preference Name Acceptable Values Preferences UI  (in bold) and comments
    advanced.mailftp false (default)
    true
    Preferences | Advanced |
    "[x] Set this email address as anonymous FTP password:"

    If false, FTP uses "mozilla@example.com" as anonymous FTP password (bug 101027)
    If true, FTP uses contents of network.ftp.anonymous_password for anonymous FTP password (bug 57763)
    network.ftp.anonymous_password empty (default)
    any text string

    Preferences  | Advanced |
    (under "[ ] Set this email address as anonymous FTP password:")
    [text field]

    If empty, FTP uses "mozilla@example.com" as anonymous FTP password.
    network.ftp.idleConnectionTimeout
    300 (default)
    any integer
    No UI
    Measured in seconds
    The open connection can prevent other FTP clients on your system from connecting to sites that allow only one control connection (bug 117875)
    network.dir.format
    0 = HTML view
    1 = raw view
    2 = HTML view
    3 = XUL view
    Preferences | Debug | Networking
    Networking
    Directory Listing Format
    ( ) HTML
    ( ) XUL (tree-based)

    Cache
    Preference Name Acceptable Values Preferences UI  (in bold) and comments
    browser.cache.disk.capacity
    51200 (default)

    Preferences | Advanced | Cache
    Cache: [MB] MB

    Stored as KB
    browser.cache.disk.parent_directory
    path to Cache folder in profile (default)
    Cache Folder: [text box]
    Note: the contents of disk and mem cache are different (a very large mem cache is not the same as pointing disk cache to memory mapped disk space (RAM disk).
    browser.cache.check_doc_frequency
    1 = Every time I view the page
    0 = Once per session
    3 = When the page is out of date (default)
    2 = Never
    Compare the page in cache to the page on the network:
    browser.cache.disk.enable
    true (default)
    Preferences  | Debug  | Cache
    [x] Enable Disk Cache
    [x] Enable Memory Cache

    Disabling disk cache has the effect of setting it to zero.
    browser.cache.memory.enable
    true (default)
    browser.cache.memory.capacity any integer (in KB)
    Replaced by automatic sizing in Mozilla 1.4b (bug 105344).
    This value overrides the application.
    0 disables feature
    (before, 4096K = default)
    network.http.use-cache true (default)
    no UI
    browser.cache.disk_cache_ssl
    false (default)
    no UI, added in 1.6a (see bug 205921)
    network.prefetch-next
    true (default)
    Preferences | Advanced | Cache:
    Link Prefetching
    [x] Prefetch web pages when idle, so that links in web page designed for prefetching can load faster.

    DNS
    Preference Name Acceptable Values Preferences UI  (in bold) and comments
    network.dnsCacheExpiration
    60 (seconds)
    default pref-less, not visible in about:config.
    Create and set both values to "0" to disable.
    network.dnsCacheEntries
    20 (entries)

    Cookies

    Please see: http://www.mozilla.org/projects/netlib/cookies/cookie-prefs.html

    The old section in this document was removed because of dwitte's cookies re-write.


    Proxy
    Preference Name Acceptable Values Preferences UI  (in bold) and comments
    network.proxy.type 0 = direct
    1 = manual
    2 = PAC
    3 -> mapped to 0
    4 = WPAD
    Preferences | Advanced | Proxies
    Configure Proxies to Access the Internet
    ( ) Direct connection to the internet
    ( ) Auto-detect proxy settings (new in 1.8):
    ( ) Manual proxy configuration
    ( ) Automatic proxy configuration URL

    3 was old Communicator value for DIRECT.
    network.proxy.http <Protocol> Proxy:
    hostname or IPv4 is acceptable.
    IPv6 needs to be tested.

    Port:
    0 will cause server:port preference for that manual proxy type to be ignored.
    1-65xxx is valid range
    Affects http: URLs
    network.proxy.http_port
    network.proxy.ssl Affects https: URLs
    Possibly affects SIMAP and SNEWS
    network.proxy.ssl_port
    network.proxy.ftp Affects ftp: URLs
    network.proxy.ftp_port
    network.proxy.gopher Affects gopher: URLs
    network.proxy.gopher_port
    network.proxy.socks Used when application-specific proxy is not configured.
    Possibly affects other protocols
    network.proxy.socks_port
    network.proxy.socks_version
    5 (default)
    4
    Communicator supported only SOCKS V4.
    network.proxy.no_proxies_on localhost, 127.0.0.1 (default)
    string of comma delimited fqdn's, hostnames, IPv4 addresses and CDIR blocks. See "No Proxy For".
    Localhost is not proxied by default, bug  31510.
    network.proxy.autoconfig_url empty (default)
    URL string
    must be absolute URl, no hostname

    Online
    network.online
    true = Mozilla is online (default)
    false = Mozilla is offline
    Necko updates the offline|online status to this value.
    Changing this value does not change the actual networking status.
    Value is not updated if "Ask me for online state at startup" was selected
    for the current profile (bug 229677).
    offline.startup_state
    0 = use network.online (default)
    1 = prompt user
    Preferences: Mail & Newsgroups | Offline | When starting up:
    (Pref affects all modules, but was moved from Pref root, bug 202529)
    [x] Remember previous online state
    (Uses network.online to set online|offline status at startup)
    [ ] Ask me for online state at startup
    (Unlike Communicator, prompt always appears, bug 239564)


    Gopher (see also Proxy)

    Name values
    Comments (bold for areas that user configures)
    network.dir.format
    see FTP

    Unsupported
    Name values
    Comments (bold for areas that user configures)
    browser.xul.error.pages.enabled
    false (default)
    true
    Does not appear in about.config unless added explicitly. See bug 28586)
    network.protocol-handler.external.SCHEME
    false (default)
    true
    Mac+Windows: sends URLs of <SCHEME> to the default OS handler
    Linux/UNIX: sends URLs to application
    For example:
    network.protocol-handler.external.mailto==true
    is used by Phoenix/Firebird/Firefox to access default mailers.
    Handlers loaded before prefs are read cannot be redirected (e.g. file:)

    Obsolete/Removed (this is list is incomplete)
    browser.cache.enable
    browser.cache.disk.directory
    networking.proxy.wais
    networking.proxy.wais_port
    network.http.connect.timeout
    network.http.proxy.ssl.connect
    Under Investigation:
    offline.startup_state