Ngx_http_trim_filter

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2023-12-01

The ngx_http_trim_filter module is a filter that modifies a response by removing unnecessary whitespaces (spaces, tabs, newlines) and comments from HTML (including inline javascript and css). Trim module parses HTML with a state machine.

location / {
    trim on;
    trim_js on;
    trim_css on;
}

Directives

trim on | off Default: trim off Context: http, server, location

Enable or disable trim module for pure HTML.

This module will retain some contents unchanged, in case that they are enclosed by the tag pre,textarea,script and style,as well as IE/SSI/ESI comments.

Parameter value can contain variables.

Example:

set $flag "off";
if ($condition) {
set $flag "on";
}
trim $flag;

trim_js on | off Default: trim_js off Context: http, server, location

Enable or disable trim module for inline javascript.

Parameter value can contain variables too.

trim_css on | off Default: trim_css off Context: http, server, location

Enable or disable trim module for inline css.

Parameter value can contain variables too.

trim_types MIME types Default: trim_types: text/html Context: http, server, location

Enable trim module for the specified MIME types in addition to "text/html". Responses with the “text/html” type are always processed.

Trim module will be disabled if incoming request has http_trim=off parameter in url.

e.g. http://www.xxx.com/index.html?http_trim=off

original:

<!DOCTYPE html>
<textarea  >
trim
module
</textarea  >
<!--remove all-->
<!--[if IE]> trim module <![endif]-->
<!--[if !IE ]>--> trim module  <!--<![endif]-->
<!--# ssi-->
<!--esi-->
<pre    style  =
"color:   blue"  >Welcome    to    nginx!</pre  >
<script type="text/javascript">
/***  muitl comment
***/
//// single comment
str.replace(/     /,"hello");
</script>
<style   type="text/css"  >
/*** css comment
! ***/
body
{
font-size:  20px ;
line-height: 150% ;
}
</style>

result:

<!DOCTYPE html>
<textarea>
trim
module
</textarea>
<!--[if IE]> trim module <![endif]-->
<!--[if !IE ]>--> trim module  <!--<![endif]-->
<!--# ssi-->
<!--esi-->
<pre style="color:   blue">Welcome    to    nginx!</pre>
<script type="text/javascript">str.replace(/     /,"hello");</script>
<style type="text/css">body{font-size:20px;line-height:150%;}</style>

Html

Whitespace

Remove '\r'.
Replace '\t' with space.
Replace multiple spaces with a single space.
Replace multiple '\n' with a single '\n'.
Replace multiple '\n' and '\t' in tag with a single space.
Do not trim quoted strings in tag.
Do not trim the contents enclosed by the tag pre,textarea,script and style.

Comment

Remove html comment().
Do not trim IE/SSI/ESI comments. IE comment:  SSI comment:  ESI comment:

Javascript

Contents enclosed by <script type="text/javascript"> or <script> will be identified as javascript.

Whitespace

Remove '\r'.
Remove '\t','\n' and space that behind '(',',','=',':','[','!','&','|','?',';','>','~','*','{'.
Replace multiple spaces with a single space.
Do not trim quoted strings and regular expression literals.

Comment

Remove single comment. //
Remove multi comment. /* */

Css

Contents enclosed by <style type="text/css"> or <style> will be identified as css.

Whiltespace

Remove '\r'.
Remove '\t','\n' and space that around ';','>','{','}',':',','.
Replace multiple '\n' and spaces with a single space.
Do not trim quoted strings.

Comment

Remove css comment(/* */).
Do not remove child seletor and IE5 /Mac hack comments. Child seletor hack: html>/**/body p{color:blue} IE5 /Mac hack: /*\*/.selector{color:khaki}/**/ `