• Skip to main content
  • Select language
  • Skip to search
MDN Web Docs
  • Technologies
    • HTML
    • CSS
    • JavaScript
    • Graphics
    • HTTP
    • APIs / DOM
    • WebExtensions
    • MathML
  • References & Guides
    • Learn web development
    • Tutorials
    • References
    • Developer Guides
    • Accessibility
    • Game development
    • ...more docs
Archive of obsolete content
  1. MDN
  2. Archive of obsolete content
  3. Plugins
  4. The First Install Problem

The First Install Problem

In This Article
    1. Problem Definition
    2. Proposed Solution
    3. Future Directions: Using OBJECT Tag with classid: Incidental Benefit

This is an old working document; see en/Gecko_Plugin_API_Reference/Plug-in_Development_Overview for current information.

Problem Definition

The First Install Problem is the name given to the conditions arising when a plugin or embeddable software installs itself on a system first, before any other Gecko-based browser. If this happens, Gecko-based browsers often won't be able to discover the plugin, and will prompt the user to download the plugin again if the affiliated MIME type is encountered on the Web. Unless Gecko does a pre-emptive scan upon startup for desirable plugins that are not in the browser's plugins directory first, the best way to solve this problem is to encourage plugin vendors to leave DLLs (and XPT files, if applicable) in a location that Gecko can discover at runtime. This document presents a consistent way to do that.

 

Proposed Solution

On Mac OS X, the System's Plugins Folder will probably suffice as an install location in which browsers installed later can find their plugins. On Linux, a per-profile installation of plugins seems unavoidable. This document presents Windows solutions for plugin vendors. The solution suggests that plugin vendors ought to leave DLLs on a Windows desktop whether or not a Netscape Gecko browser is detected, and then write keys in the Windows registry giving future Netscape Gecko browsers the path where the plugin resides and meta-information about how to load the plugin. This document supplements the key parsing methodology suggested for installers. The solution is to encourage plugin vendors to write registry keys to the Win32 System Registry, like the example application.

This document proposes a meta-information model in the Win32 Registry similar to the one used by Microsoft's HKEY_CLASSES_ROOT\CLSID\ where a new ActiveX control (OCX) on the system presents its UUID as a registry key (identifying the ActiveX control) as well as information about where to find the OCX (e.g. under the InprocServer32 subkey). For Mozilla-based browsers, this system would be on a per-module basis, and instead of a UUID, we'll use a URI nomenclature that gives us the desired uniqueness. This URI nomenclature is called a Plugin Identifier (PLID) and is described on a separate page. The following write-up describes how a plugin installer can write keys to the Win32 System Registry to enable Gecko-based browsers to discover the plugin at runtime.

  1. Write a key under HKEY_LOCAL_MACHINE\Software\MozillaPlugins\ which is a vendor-determined PLID. If the HKEY_LOCAL_MACHINE\Software\MozillaPlugins key doesn't exist, create it, and write the vendor-determined PLID for each module that the vendor wishes to install. Example: A piece of software called MyApplication might create HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.0.1/ where the PLID is something the corporation that makes MyApplication (MyCompany Inc.) determines. Note that MyApplication consists of one DLL (which is an NPAPI plugin handling a given mimetype -- say application/x-myapp) and one XPT file, for scriptable interfaces.
  2. Caveat Emptor: If the key cannot be created under HKEY_LOCAL_MACHINE, create it as HKEY_CURRENT_USER\Software\MozillaPlugins\ under HKEY_CURRENT_USER. On Windows XP and Windows 2000, in order to write to the registry, sometimes the software may need Administrator privileges. Thus, some installers may need to write to the HKEY_CURRENT_USER key; this doesn't require Administrator privileges. Traditionally, HKEY_CURRENT_USER is a copy of everything in HKEY_LOCAL_MACHINE. At present plugins registered using the HKEY_CURRENT_USER\Software\MozillaPlugins\ tree are ignored by Firefox (bug 293062) but this is fixed in trunk builds (bug 293062).
  3. Add the following Values to the newly created key -- some are String Values (REG_SZ), and some are actually subkeys. String Values take the form StringValue=ValueData, and subkeys contain their own String Values and Value data.
    • "Path" -- String Value -- this would be the absolute path to the plugin module. This is the path to the actual DLL. (Note that the file name must still begin with "np", just as it must when the file is loaded from the .\plugins directory.)
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01]
      Path=C:\MyCompany\MyApplication\Netscape\npmyapp.dll
    • "XPTPath" -- String Value -- absolute path to xpt module required for scripting plug-in, if applicable
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01]
      XPTPath=C:\MyCompany\MyApplication\Netscape\npmyapp.xpt
    • "GeckoVersion" -- This is the optional mention of the minimal Gecko Version that the browser is compatible with.
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01]
      GeckoVersion=0.9.4.2
      suggesting compliance with CompuServe's deployment of a build of Gecko known as 0.9.4.2. Note that this means that at a minimum, the plugin vendor is ensuring compatibility with 0.9.4.2 browsers.
    • "ProductName" -- This is the String Value name of the actual product.
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01]
      ProductName=MyApplication Player 5
    • "Version" -- This is the versioning scheme of the above Product.
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01]
      Version=5.01
    • MimeTypes -- This is a subkey and contains individual mimetypes as further subkeys.
      HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01/MimeTypes/someMimeTypeSubkey/
      • The MimeTypes subkey contains further subkeys based on an application's actual mimetypes.
        Examples:
        [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01\MimeTypes\application/x-myapp]

        There can be more than one such subkey, depending on how many mimetypes an application wishes to handle (or advertise that it handles).

      • The mimetypes subkeys contain the following string (REG_SZ) value:
        • "Description" -- This is the actual description of the mimetype, very much as it appears in the DLL (e.g. the same mimetype description that apears when you type "about:plugins" as a URL in Mozilla's location bar.
          Example:
          [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\]\@mycompany.com/MyApplication,version=5.01\MimeTypes\application/x-myapp]
          Description=MyApplication   Plugin for App Files
        • "Suffixes" -- This will be a semi-colon concatenated list of supported suffixes. This information is also stored under the Suffixes subkey (see below), but that key doesn't link suffixes to a particular mimetype.
          Example:
          [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\]\@mycompany.com/MyApplication,version=5.01\MimeTypes\application/x-myapp]
          Suffixes=app
    • Suffixes -- a subkey containing string values (REG_SZ) representing all the suffixes (3 digit extensions) supported by this module.
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\]\@mycompany.com/MyApplication,version=5.01\Suffixes]

      Inside this subkey, string values might look like:
      app
      typ
      avi

      Note that these string values (REG_SZ) don't actually have values affiliated with them.

    • "Description" -- string value describing the module (distinct from the "Description" in the MimeTypes subkey).
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01] 
      Description=Scriptable MyApplication Player Version 5
    • "Vendor" -- string refering to company name
      Example:
      [HKEY_LOCAL_MACHINE\Software\MozillaPlugins\@mycompany.com/MyApplication,version=5.01] 
      Vendor=MyCompany   Inc.

The example registry key shows the suggested "key creation" at work for an example application called Scobe Scrubobat (which doesn't really exist!).

 

Future Directions: Using OBJECT Tag with classid: Incidental Benefit

Embedders such as CompuServe (who now embed Gecko in lieu of IE as the default browser) can determine on their own the mechanisms to parse the Win32 registry for PLIDs. The Bugzilla bug open on Mozilla and Netscape 6.x is bug 44973.

If every major plugin vendor complies with the writing of plugin directory information into the registry along with a PLID, we can then use the OBJECT tag to invoke plugins based on their "classid" (their respective PLID, which is a URI, which works well with the W3C spec). For example, in our case, a prospective invocation might look like:

  <object classid="@mycompany.com/MyApplication,version=5.01" 
          data="myfile.typ" codebase="http://myurl.com/myplugin/myplugin.xpi" 
          type="application/x-myapp"></object>

The use of both "type" and "classid" attributes here offers the following user benefit:

  • IF there is another mimetype handler for application/x-myapp, ONLY MyApplication gets invoked. The resolution of a mimetype handler is no longer arbitrary.
  • IF the "data" file myfile.typ doesn't contain enough resource information to load the correct mimetype handling component (DLL), specifying "type" is an additional mechanism.
  • Unlike UUIDs, PLIDs are human readable, and not lengthy "garbled" strings.

(It should be noted that the "classid" attribute discussion here is a potential future direction; it doesn't yet work, at least as of Firefox 3.6.8. The recommended <object> attribute to set is still either "type" or "data".)

Advantage: We now no longer have ambiguity in determining which plugin handles what mimetype, because now the plugin has been invoked using the classid attribute of the OBJECT tag, which is in compliance with the HTML 4.01 specification for use of the OBJECT tag.

(Original proposal by Arun K. Ranganathan <aruner@netscape.com>)

Document Tags and Contributors

Tags: 
  • Add-ons
  • Plugins
 Contributors to this page: teoli, wbamberg, Naesten, jswisher, smithkl42, bsittler, Sheppy, Josh, Nickolay
 Last updated by: teoli, Mar 15, 2017, 4:47:45 AM

  1. .htaccess ( hypertext access )
  2. <input> archive
  3. Add-ons
    1. Add-ons
    2. Firefox addons developer guide
    3. Interaction between privileged and non-privileged pages
    4. Tabbed browser
    5. bookmarks.export()
    6. bookmarks.import()
  4. Adding preferences to an extension
  5. An Interview With Douglas Bowman of Wired News
  6. Apps
    1. Apps
    2. App Development API Reference
    3. Designing Open Web Apps
    4. Graphics and UX
    5. Open web app architecture
    6. Tools and frameworks
    7. Validating web apps with the App Validator
  7. Archived Mozilla and build documentation
    1. Archived Mozilla and build documentation
    2. ActiveX Control for Hosting Netscape Plug-ins in IE
    3. Archived SpiderMonkey docs
    4. Autodial for Windows NT
    5. Automated testing tips and tricks
    6. Automatic Mozilla Configurator
    7. Automatically Handle Failed Asserts in Debug Builds
    8. BlackConnect
    9. Blackwood
    10. Bonsai
    11. Bookmark Keywords
    12. Building TransforMiiX standalone
    13. Chromeless
    14. Creating a Firefox sidebar extension
    15. Creating a Microsummary
    16. Creating a Mozilla Extension
    17. Creating a Release Tag
    18. Creating a Skin for Firefox/Getting Started
    19. Creating a Skin for Mozilla
    20. Creating a Skin for SeaMonkey 2.x
    21. Creating a hybrid CD
    22. Creating regular expressions for a microsummary generator
    23. DTrace
    24. Dehydra
    25. Developing New Mozilla Features
    26. Devmo 1.0 Launch Roadmap
    27. Download Manager improvements in Firefox 3
    28. Download Manager preferences
    29. Drag and Drop
    30. Embedding FAQ
    31. Embedding Mozilla in a Java Application using JavaXPCOM
    32. Error Console
    33. Exception logging in JavaScript
    34. Existing Content
    35. Extension Frequently Asked Questions
    36. Fighting Junk Mail with Netscape 7.1
    37. Firefox Sync
    38. Force RTL
    39. GRE
    40. Gecko Coding Help Wanted
    41. HTTP Class Overview
    42. Hacking wiki
    43. Help Viewer
    44. Helper Apps (and a bit of Save As)
    45. Hidden prefs
    46. How to Write and Land Nanojit Patches
    47. Introducing the Audio API extension
    48. Java in Firefox Extensions
    49. JavaScript crypto
    50. Jetpack
    51. Litmus tests
    52. Makefile.mozextension.2
    53. Microsummary topics
    54. Migrate apps from Internet Explorer to Mozilla
    55. Monitoring downloads
    56. Mozilla Application Framework
    57. Mozilla Crypto FAQ
    58. Mozilla Modules and Module Ownership
    59. Mozprocess
    60. Mozprofile
    61. Mozrunner
    62. Nanojit
    63. New Skin Notes
    64. Persona
    65. Plug-n-Hack
    66. Plugin Architecture
    67. Porting NSPR to Unix Platforms
    68. Priority Content
    69. Prism
    70. Proxy UI
    71. Remote XUL
    72. SXSW 2007 presentations
    73. Space Manager Detailed Design
    74. Space Manager High Level Design
    75. Standalone XPCOM
    76. Stress testing
    77. Structure of an installable bundle
    78. Supporting private browsing mode
    79. Table Cellmap
    80. Table Cellmap - Border Collapse
    81. Table Layout Regression Tests
    82. Table Layout Strategy
    83. Tamarin
    84. The Download Manager schema
    85. The life of an HTML HTTP request
    86. The new nsString class implementation (1999)
    87. TraceVis
    88. Treehydra
    89. URIScheme
    90. URIs and URLs
    91. Using Monotone With Mozilla CVS
    92. Using SVK With Mozilla CVS
    93. Using addresses of stack variables with NSPR threads on win16
    94. Venkman
    95. Video presentations
    96. Why Embed Gecko
    97. XML in Mozilla
    98. XPInstall
    99. XPJS Components Proposal
    100. XRE
    101. XTech 2005 Presentations
    102. XTech 2006 Presentations
    103. XUL Explorer
    104. XULRunner
    105. ant script to assemble an extension
    106. calICalendarView
    107. calICalendarViewController
    108. calIFileType
    109. xbDesignMode.js
  8. Archived open Web documentation
    1. Archived open Web documentation
    2. Browser Detection and Cross Browser Support
    3. Browser Feature Detection
    4. Displaying notifications (deprecated)
    5. E4X
    6. E4X Tutorial
    7. LiveConnect
    8. MSX Emulator (jsMSX)
    9. Old Proxy API
    10. Properly Using CSS and JavaScript in XHTML Documents
    11. Reference
    12. Scope Cheatsheet
    13. Server-Side JavaScript
    14. Sharp variables in JavaScript
    15. Standards-Compliant Authoring Tools
    16. Using JavaScript Generators in Firefox
    17. Window.importDialog()
    18. Writing JavaScript for XHTML
    19. XForms
    20. background-size
    21. forEach
  9. B2G OS
    1. B2G OS
    2. Automated Testing of B2G OS
    3. B2G OS APIs
    4. B2G OS add-ons
    5. B2G OS architecture
    6. B2G OS build prerequisites
    7. B2G OS phone guide
    8. Building B2G OS
    9. Building and installing B2G OS
    10. Building the B2G OS Simulator
    11. Choosing how to run Gaia or B2G
    12. Customization with the .userconfig file
    13. Debugging on Firefox OS
    14. Developer Mode
    15. Developing Firefox OS
    16. Firefox OS Simulator
    17. Firefox OS apps
    18. Firefox OS board guide
    19. Firefox OS developer release notes
    20. Firefox OS security
    21. Firefox OS usage tips
    22. Gaia
    23. Installing B2G OS on a mobile device
    24. Introduction to Firefox OS
    25. Mulet
    26. Open web apps quickstart
    27. Pandaboard
    28. PasscodeHelper Internals
    29. Porting B2G OS
    30. Preparing for your first B2G build
    31. Resources
    32. Running tests on Firefox OS: A guide for developers
    33. The B2G OS platform
    34. Troubleshooting B2G OS
    35. Using the App Manager
    36. Using the B2G emulators
    37. Web Bluetooth API (Firefox OS)
    38. Web Telephony API
    39. Web applications
  10. Beginner tutorials
    1. Beginner tutorials
    2. Creating reusable content with CSS and XBL
    3. Underscores in class and ID Names
    4. XML data
    5. XUL user interfaces
  11. Case Sensitivity in class and id Names
  12. Creating a dynamic status bar extension
  13. Creating a status bar extension
  14. Gecko Compatibility Handbook
  15. Getting the page URL in NPAPI plugin
  16. Index
  17. Inner-browsing extending the browser navigation paradigm
  18. Install.js
  19. JXON
  20. List of Former Mozilla-Based Applications
  21. List of Mozilla-Based Applications
  22. Localizing an extension
  23. MDN
    1. MDN
    2. Content kits
  24. MDN "meta-documentation" archive
    1. MDN "meta-documentation" archive
    2. Article page layout guide
    3. Blog posts to integrate into documentation
    4. Current events
    5. Custom CSS classes for MDN
    6. Design Document
    7. DevEdge
    8. Developer documentation process
    9. Disambiguation
    10. Documentation Wishlist
    11. Documentation planning and tracking
    12. Editing MDN pages
    13. Examples
    14. Existing Content/DOM in Mozilla
    15. External Redirects
    16. Finding the right place to document bugs
    17. Getting started as a new MDN contributor
    18. Landing page layout guide
    19. MDN content on WebPlatform.org
    20. MDN page layout guide
    21. MDN subproject list
    22. Needs Redirect
    23. Page types
    24. RecRoom documentation plan
    25. Remove in-content iframes
    26. Team status board
    27. Trello
    28. Using the Mozilla Developer Center
    29. Welcome to the Mozilla Developer Network
    30. Writing chrome code documentation plan
    31. Writing content
  25. MMgc
  26. Makefile - .mk files
  27. Marketplace
    1. Marketplace
    2. API
    3. Monetization
    4. Options
    5. Publishing
  28. Mozilla release FAQ
  29. Newsgroup summaries
    1. Newsgroup summaries
    2. Format
    3. Mozilla.dev.apps.firefox-2006-09-29
    4. Mozilla.dev.apps.firefox-2006-10-06
    5. mozilla-dev-accessibility
    6. mozilla-dev-apps-calendar
    7. mozilla-dev-apps-firefox
    8. mozilla-dev-apps-thunderbird
    9. mozilla-dev-builds
    10. mozilla-dev-embedding
    11. mozilla-dev-extensions
    12. mozilla-dev-i18n
    13. mozilla-dev-l10n
    14. mozilla-dev-planning
    15. mozilla-dev-platform
    16. mozilla-dev-quality
    17. mozilla-dev-security
    18. mozilla-dev-tech-js-engine
    19. mozilla-dev-tech-layout
    20. mozilla-dev-tech-xpcom
    21. mozilla-dev-tech-xul
    22. mozilla.dev.apps.calendar
    23. mozilla.dev.tech.js-engine
  30. Obsolete: XPCOM-based scripting for NPAPI plugins
  31. Plugins
    1. Plugins
    2. Adobe Flash
    3. External resources for plugin creation
    4. Logging Multi-Process Plugins
    5. Monitoring plugins
    6. Multi-process plugin architecture
    7. NPAPI plugin developer guide
    8. NPAPI plugin reference
    9. Samples and Test Cases
    10. Shipping a plugin as a Toolkit bundle
    11. Supporting private browsing in plugins
    12. The First Install Problem
    13. Writing a plugin for Mac OS X
    14. XEmbed Extension for Mozilla Plugins
  32. SAX
  33. Security
    1. Security
    2. Digital Signatures
    3. Encryption and Decryption
    4. Introduction to Public-Key Cryptography
    5. Introduction to SSL
    6. NSPR Release Engineering Guide
    7. SSL and TLS
  34. Solaris 10 Build Prerequisites
  35. Sunbird Theme Tutorial
  36. Table Reflow Internals
  37. Tamarin Tracing Build Documentation
  38. The Basics of Web Services
  39. Themes
    1. Themes
    2. Building a Theme
    3. Common Firefox theme issues and solutions
    4. Creating a Skin for Firefox
    5. Making sure your theme works with RTL locales
    6. Theme changes in Firefox 2
    7. Theme changes in Firefox 3
    8. Theme changes in Firefox 3.5
    9. Theme changes in Firefox 4
  40. Updating an extension to support multiple Mozilla applications
  41. Using IO Timeout And Interrupt On NT
  42. Using SSH to connect to CVS
  43. Using workers in extensions
  44. WebVR
    1. WebVR
    2. WebVR environment setup
  45. XQuery
  46. XUL Booster
  47. XUL Parser in Python