Status of this document
This is a major revision of the original, obsolete, user-agent string proposal. See the discussions on netscape.public.mozilla.seamonkey and netscape.public.mozilla.netlib for background information.
This document is the official Mozilla user-agent string specification. However, the following issues are under review and may be revised in the near future:
- The requirement for a three-digit
Minorversion number has not yet been tested on the web because there has not yet been a "point release" of Mozilla. Thus there is a chance that this may need to be changed.
- There is concern that the attempt to separate
OS-or-CPUon Windows and Macintosh is not backwards compatible and the user-agent strings should return to their old-fashioned form.
- There is concern that giving the operating system version on Windows reveals too much information about a system (such as potential security holes).
- There is concern that revealing localization information is a violation of privacy.
The original goals:
- Obey the standard described in RFC 1945 and RFC 2068.
- Don't break existing web servers.
- Don't break existing log-file analysis software or user-agent parsing code.
- Keep the User-Agent string reasonably short.
- Use a consistent, obvious, and easy-to-parse format.
Other concerns that came out of discussion:
- Provide date-based version information.
- Address the issue of version modifiers.
- Provide a way for applications that contain Mozilla technology (i.e. Gecko) but are not Mozilla to identify themselves
For browsers based on Mozilla, the user-agent string shall follow the format:
MozillaProductToken (MozillaComment) GeckoProductToken *(VendorProductToken|VendorComment)
Applications that embed the Gecko layout engine shall have user-agent strings that follow the format:
ApplicationProductToken (ApplicationComment) GeckoProductToken *(VendorProductToken|VendorComment)
|MozillaVersion||Major . minor|
|Major||Integer indicating major release number.|
|Minor||If non-zero, it shall be a three-digit, zero-filled number, i.e. 001. If zero, zero is fine.|
|MozillaComment||( Platform ; Security ; OS-or-CPU ; Localization information ?[; PrereleaseVersion] ) *[; Optional Other Comments] )|
|Platform|| Allowed values:
|Security|| Allowed values:
Values for Windows systems:
|Localization Information|| Language Tag as described in the standards RFC 1945 and RFC 2068.
en, en-US, es, es-CO, ja, ja-JP, etc.
|PrereleaseVersion||String whose first character is [a-zA-Z]. By convention, used to indicate pre-release versions, such as beta quality software, or milestones. This should not be present in final release software.|
The Gecko product token allows products that embed the Gecko engine, including Mozilla, to identify this significant sub-product.
|GeckoVersion||Date in the format YYYYMMDD. For official Mozilla builds, this will correspond to the date portion of the BuildID. For branded versions of Mozilla, the GeckoVersion should correspond to the date the code was pulled from mozilla.org, and may not necessarily correspond to the date portion of the generated BuildID.|
|ApplicationProductToken, Application Comment||For use by applications that embed Gecko layout engine. The form of their product token and comment is not specified here, but should adhere to the HTTP standards.|
|( VendorProductToken | VendorComment )||Product tokens for applications based on Mozilla. Format and content shall be vendor-specific, but should adhere to the HTTP standards.|
|*||Zero or more of the following token are allowed.|
|?||Zero or one of the following token are allowed.|
|A mozilla.org release||Mozilla/5.001 (windows; U; NT4.0; en-us) Gecko/25250101|
|A branded release based on the same codebase as the browser above||Mozilla/5.001 (Macintosh; N; PPC; ja) Gecko/25250101 MegaCorpBrowser/1.0 (MegaCorp, Inc.)|
|A re-branded release||Mozilla/9.876 (X11; U; Linux 2.2.12-20 i686, en) Gecko/25250101 Netscape/5.432b1 (C-MindSpring)|
|A Gecko-based browser||TinyBrowser/2.0 (TinyBrowser Comment) Gecko/20201231|
Implementation notes for applications, vendors, and extensions
Starting with Mozilla 1.8 beta2, the best way for applications,
vendors, and extensions (if needed) to add to default preferences to
to add a default preference of the form
general.useragent.extra.* preferences will have
their string values added to the User-Agent string in alphabetical
order by identifier. For example:
pref("general.useragent.extra.megabrowser", "MegaCorpBrowser/1.0 (MegaCorp, Inc.)");
Comments to netscape.public.mozilla.netlib or email@example.com