proxies on

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As browsers rapidly grew in popularity in the mid-90's, many network administrators added proxy servers. Initially, proxy servers were used for access control and performance. Many networks had limited access to the public network via proxy servers. Because the public network was small in scope and connections were slow, a caching proxy could often improve the overall performance.

This preferencewas originally designed as a "blacklist" of sites or domains that was within the intranet, and should not be accessed via the proxy server. Due to various limitations, this preference should be used for only the most simple blacklist scenarios. In almost all cases, PAC gives better control and flexibility.

Possible values and their effects

The no proxy list is composed of either domain elements or IPv4 address elements. The elements are separated by either a space (" ") or a comma (","). (Default: localhost,

Note for former-IE users: "*" is supported only at the beginning of domain filters (*

To block a... put this into "No Proxy for" ...for example use... Limitations
domain, including sub-domains domain suffix, starting with a dot "," You must use both entries to block a single domain.
hostname (without domain) hostname-only (see problems below) "local host" Also blocks any possible domains that start with the entry ("www.otherdomain.localhost")
hostname (with domain) domain name "" Also blocks any hostnames or domains that end in the same string (
IP address IP address "" Does not block hostnames that resolve to the IP address ("" does not block "local host")
Network network w/ CIDR block "" Does not block hostnames that resolve to the IP address range ( is not no proxy for intranets)
optional - port-specific (optional) ":" + port number "<FILTER>:81" Only black-lists port. Only applies to one port (no support for ranges and/or multiple ports).

Port-only filters ":80" or "*:80" are not supported.

Formats that are not accepted Example
Domain filters with interior wildcards www.*.com
IP address string prefixes 127. or 10.0.*
IP addresses with wildcards in quads 10.*.*.*


  • No IPv6 support - The backend stores IPv4 addresses as IPv6, but IPv6 formats are not supported.
  • Scalability - Not usable for localdomains with numerous hostnames. Not usable for large number of filters (ad blocking).
  • Mozilla implements this feature with significant limitations, users may find that writing a PAC file is more suitable for their needs.



Tools -> Options -> General -> Connection Settings... -> No proxy for

Mozilla Suite


First checked in

Exact check-in date unknown. Present since at least 2000-02-14.

Has an effect in

  • Netscape (all versions since at least 6.0)
  • Mozilla Suite (all versions)
  • Mozilla Firefox (all versions)
  • SeaMonkey (all versions)
  • Camino (all versions)
  • Minimo (all versions)

Related preferences

Related bugs