How does RewriteBase work in htaccess

Question

I have seen this in a few  htaccess examples  RewriteBase     It appears to be somewhat similar in functionality to the  lt base href    gt  of HTML    I believe it may automatically prepend its value to the beginning of RewriteRule statements  possibly ones without a leading slash    I could not get it to work properly  I think it s use could come in very handy for site portability  as I often have a development server which is different to a production one  My current method leaves me deleting portions out of my RewriteRule statements   Can anyone explain to me briefly how to implement it   Thanks

User · Answer

The clearest explanation I found was not in the current 2.4 apache docs, but in version 2.0.

#  /abc/def/.htaccess -- per-dir config file for directory /abc/def
#  Remember: /abc/def is the physical path of /xyz, i.e., the server
#            has a 'Alias /xyz /abc/def' directive e.g.

RewriteEngine On

#  let the server know that we were reached via /xyz and not
#  via the physical path prefix /abc/def
RewriteBase   /xyz

How does it work? For you apache hackers, this 2.0 doc goes on to give "detailed information about the internal processing steps."

Lesson learned: While we need to be familiar with "current," gems can be found in the annals.

User · Answer

RewriteBase is only applied to the target of a relative rewrite rule    Using RewriteBase like this     RewriteBase  folder  RewriteRule a  html b html  is essentially the same as     RewriteRule a  html  folder b html  But when the  htaccess file is inside  folder  then this also points to the same target   RewriteRule a  html b html    Although the docs imply always using a RewriteBase  Apache usually detects it correctly for paths under the DocumentRoot unless    You are using Alias directives You are using  htaccess rewrite rules to perform HTTP redirects  rather than just silent rewriting  to relative URLs   In these cases  you may find that you need to specify the RewriteBase   However  since it s a confusing directive  it s generally better to simply specify absolute  aka  root relative   URIs in your rewrite targets   Other developers reading your rules will grasp these more easily       Quoting from Jon Lin s excellent in-depth answer here   In an htaccess file  mod rewrite works similar to a  lt Directory gt  or  lt Location gt  container  and the RewriteBase is used to provide a relative path base   For example  say you have this folder structure   DocumentRoot  -- subdir1  -- subdir2      -- subsubdir   So you can access    http   example com    root  http   example com subdir1   subdir1  http   example com subdir2   subdir2  http   example com subdir2 subsubdir   subsubdir    The URI that gets sent through a RewriteRule is relative to the directory containing the htaccess file  So if you have   RewriteRule        -     In the root htaccess  and the request is  a b c d  then the captured URI   1  is a b c d   If the rule is in subdir2 and the request is  subdir2 e f g then the captured URI is e f g   If the rule is in the subsubdir  and the request is  subdir2 subsubdir x y z  then the captured URI is x y z     The directory that the rule is in has that part stripped off of the URI  The rewrite base has no affect on this  this is simply how per-directory works   What the rewrite base does do  is provide a URL-path base  not a file-path base  for any relative paths in the rule s target  So say you have this rule   RewriteRule  foo  bar php  L    The bar php is a relative path  as opposed to   RewriteRule  foo   bar php  L    where the  bar php is an absolute path  The absolute path will always be the  root   in the directory structure above   That means that regardless of whether the rule is in the  root    subdir1    subsubdir   etc  the  bar php path always maps to http   example com bar php    But the other rule  with the relative path  it s based on the directory that the rule is in  So if  RewriteRule  foo  bar php  L    is in the  root  and you go to http   example com foo  you get served http   example com bar php  But if that rule is in the  subdir1  directory  and you go to http   example com subdir1 foo  you get served http   example com subdir1 bar php  etc  This sometimes works and sometimes doesn t  as the documentation says  it s supposed to be required for relative paths  but most of the time it seems to work  Except when you are redirecting  using the R flag  or implicitly because you have http   host in your rule s target   That means this rule   RewriteRule  foo  bar php  L R    if it s in the  subdir2  directory  and you go to http   example com subdir2 foo  mod rewrite will mistake the relative path as a file-path instead of a URL-path and because of the R flag  you ll end up getting redirected to something like  http   example com var www localhost htdocs subdir1  Which is obviously not what you want   This is where RewriteBase comes in  The directive tells mod rewrite what to append to the beginning of every relative path  So if I have   RewriteBase  blah  RewriteRule  foo  bar php  L    in  subsubdir   going to http   example com subdir2 subsubdir foo will actually serve me http   example com blah bar php  The  bar php  is added to the end of the base  In practice  this example is usually not what you want  because you can t have multiple bases in the same directory container or htaccess file   In most cases  it s used like this   RewriteBase  subdir1  RewriteRule  foo  bar php  L    where those rules would be in the  subdir1  directory and  RewriteBase  subdir2 subsubdir  RewriteRule  foo  bar php  L    would be in the  subsubdir  directory   This partly allows you to make your rules portable  so you can drop them in any directory and only need to change the base instead of a bunch of rules  For example if you had   RewriteEngine On RewriteRule  foo   subdir1 bar php  L  RewriteRule  blah1   subdir1 blah php id 1  L  RewriteRule  blah2   subdir1 blah2 php  L        such that going to http   example com subdir1 foo will serve http   example com subdir1 bar php etc  And say you decided to move all of those files and rules to the  subsubdir  directory  Instead of changing every instance of  subdir1  to  subdir2 subsubdir   you could have just had a base   RewriteEngine On RewriteBase  subdir1  RewriteRule  foo  bar php  L  RewriteRule  blah1  blah php id 1  L  RewriteRule  blah2  blah2 php  L        And then when you needed to move those files and the rules to another directory  just change the base   RewriteBase  subdir2 subsubdir    and that s it

User · Answer

AFAIK  RewriteBase is only used to fix cases where mod rewrite is running in a  htaccess file not at the root of a site and it guesses the wrong web path  as opposed to filesystem path  for the folder it is running in  So if you have a RewriteRule in a  htaccess in a folder that maps to http   example com myfolder you can use   RewriteBase myfolder   If mod rewrite isn t working correctly   Trying to use it to achieve something unusual  rather than to fix this problem sounds like a recipe to getting very confused

User · Answer

RewriteBase is only useful in situations where you can only put a  htaccess at the root of your site  Otherwise  you may be better off placing your different  htaccess files in different directories of your site and completely omitting the RewriteBase directive   Lately  for complex sites  I ve been taking them out  because it makes deploying files from testing to live just one more step complicated

User · Answer

I believe this excerpt from the Apache documentation  complements well the previous answers        This directive is required when you use a relative path in a   substitution in per-directory  htaccess  context unless either of the   following conditions are true          The original request  and the substitution  are underneath the DocumentRoot  as opposed to reachable by other means  such as Alias     The filesystem path to the directory containing the RewriteRule  suffixed by the relative substitution is also valid as a URL path on   the server  this is rare           As previously mentioned  in other contexts  it is only useful to make   your rule shorter  Moreover  also as previously mentioned  you can   achieve the same thing by placing the htaccess file in the   subdirectory

User · Answer

When I develop  it s on a different domain within a folder   When I take a site live  that folder doesn t exist anymore   Using RewriteBase allows me to use the same  htaccess file in both environments    When live   RewriteBase     RewriteBase  dev folder    When developing     RewriteBase   RewriteBase  dev folder

User · Answer

In my own words  after reading the docs and experimenting   You can use RewriteBase to provide a base for your rewrites  Consider this    invoke rewrite engine     RewriteEngine On     RewriteBase   new     add trailing slash if missing     rewriteRule     a-z0-9 -      a-z0-9 -      1   NC R 301 L    This is a real rule I used to ensure that URLs have a trailing slash   This will convert   http   www example com  new page   to   http   www example com  new page    By having the RewriteBase there  you make the relative path come off the RewriteBase parameter

User · Answer

This command can explicitly set the base URL for your rewrites  If you wish to start in the root of your domain  you would include the following line before your RewriteRule   RewriteBase

[.htaccess] How does RewriteBase work in .htaccess

Examples related to .htaccess

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