Start the Dynamic HTML Help System


This function starts the internal help server, so that HTML help pages are rendered when requested.





logical: whether to start or shut down the dynamic help system. If NA, the server is started if not already running.


This function starts the internal HTTP server, which runs on the loopback interface ( If options("help.ports") is set to a vector of non-zero integer values, startDynamicHelp will try those ports in order; otherwise, it tries up to 10 random ports to find one not in use. It can be disabled by setting the environment variable R_DISABLE_HTTPD to a non-empty value or options("help.ports") to 0.

startDynamicHelp is called by functions that need to use the server, so would rarely be called directly by a user.

Note that options(help_type = "html") must be set to actually make use of HTML help, although it might be the default for an R installation.

If the server cannot be started or is disabled, help.start will be unavailable and requests for HTML help will give text help (with a warning).

The browser in use does need to be able to connect to the loopback interface: occasionally it is set to use a proxy for HTTP on all interfaces, which will not work – the solution is to add an exception for


The chosen port number is returned invisibly (which will be 0 if the server has been stopped).

See Also

help.start and help(help_type = "html") will attempt to start the HTTP server if required

Rd2HTML is used to render the package help pages.

Want to suggest features or report bugs for Use the GitHub issue tracker.

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