Permalinks are the permanent URLs to your individual weblog posts, as well as categories and other lists of weblog postings. A permalink is what another weblogger will use to link to your article (or section), or how you might send a link to your story in an e-mail message. The URL to each post should be permanent, and never change — hence permalink.

Permalink Types

There are three basic types of WordPress permalinks:

Default: "Ugly"

The default looks like

http://example.com/?p=N

where N is the Post ID number. It works on all server environments, but it doesn't look as nice as some of the other options.

mod_rewrite: "Pretty Permalinks"

Using mod_rewrite or lighttpd you can produce much nicer permalinks (see Pretty Permalinks). There are many different formats, but the most common, and most versatile looks like

    http://example.com/category/post-name/
or  http://example.com/year/month/day/post-name

Some people eliminate some or all of the date elements (day, month, year) to have a shorter permalink format.

Pretty permalinks are available under

• Apache web server with the mod_rewrite module
• Microsoft IIS 7+ web server with the URL Rewrite 1.1+ module and PHP 5 running as FastCGI
• Microsoft IIS 6+ using ASAPI_Rewrite
• Lighttpd using a 404 handler or mod_rewrite or mod_magnet (see External sources)

PATHINFO: "Almost Pretty"

PATHINFO permalinks look very much like mod_rewrite permalinks but for one exception: they have /index.php inserted before them, like so:

http://example.com/index.php/yyyy/mm/dd/post-name/

Otherwise, they are the same as the "pretty" mod_rewrite permalinks, and are similarly flexible. Anything that mod_rewrite permalinks can do, PATHINFO permalinks can do, with the help of that /index.php part.

There is a helpful plugin that displays the type of permalinks being used and detailed information on the internal rewrite rules used by WordPress.

Choosing your permalink structure

In the Settings ? Permalinks panel (Options ? Permalinks before WordPress 2.5), you can choose one of the "common" structures or enter your own in the "Custom structure" field using the structure tags.

Please note: You never, ever put your site url in the permalinks slot. You must use one of the structure tags, or a combination of tags only.

To activate PATHINFO permalinks, start your permalink structure with index.php/.

Structure Tags

Please note:

You never, ever put your site url in the permalinks slot. You must use one of the structure tags, or a combination of tags only. 

You can use these tags to customize your "Pretty" or "Almost Pretty" permalinks. A few hints:

• Make sure to end your structure with either %post_id% or %postname% (e.g. /%year%/%monthnum%/%day%/%postname%/) so that each permalink points to an individual post.
• For performance reasons, it is not a good idea to start your permalink structure with the category, tag, author, or postname fields. The reason is that these are text fields, and using them at the beginning of your permalink structure it takes more time for WordPress to distinguish your Post URLs from Page URLs (which always use the text "page slug" as the URL), and to compensate, WordPress stores a lot of extra information in its database (so much that sites with lots of Pages have experienced difficulties). So, it is best to start your permalink structure with a numeric field, such as the year or post ID. See wp-testers discussion of this topic.

%year%

The year of the post, four digits, for example 2004

%monthnum%

Month of the year, for example 05

%day%

Day of the month, for example 28

%hour%

Hour of the day, for example 15

%minute%

Minute of the hour, for example 43

%second%

Second of the minute, for example 33

%postname%

A sanitized version of the title of the post (post slug field on Edit Post/Page panel). So “This Is A Great Post!” becomes this-is-a-great-post in the URI (see Using only %postname%). Starting Permalinks with %postname% is strongly not recommended for performance reasons.. *** Note - this has been changed and is ok to do since ver. 2.0

%post_id%

The unique ID # of the post, for example 423

%category%

A sanitized version of the category name (category slug field on New/Edit Category panel). Nested sub-categories appear as nested directories in the URI. Starting Permalinks with %category% is strongly not recommended for performance reasons.

%tag%

A sanitized version of the tag name (tag slug field on New/Edit Tag panel). Starting Permalinks with %tag% is strongly not recommended for performance reasons.

%author%

A sanitized version of the author name.

Category base and Tag base

The Category base and Tag base are prefixes used in URLs for category and tag archives, which look like this:

 example.net/wp/category_base/category_name
 example.net/wp/tag_base/tag_name

The default values for these are category and tag. You can change them, but you can't remove them from the URLs altogether.

Custom permalinks work on most systems without any problems, but there are still some conditions where problems occur.