Resolve 500 Internal Server Error

In this Article

If there is one thing we’d hate to happen, it would be for you to install WP Rocket and face a cryptic error message announcing a “500 Internal Server Error” where your website should be appearing in a blaze of glory.

We hate it when that happens, but sometimes, under circumstances, we have no control over, it does happen. Here is what you can do about it.

Debugging

Backup .htaccess

The first thing you have to do is to connect via your FTP client and find the .htaccess file for your site. It usually can be found in the root of your server, or your WordPress install. Create a backup of that file, by copying the existing version and renaming it. 

In the original file, remove all of the WP Rocket rules, leaving only the default WordPress rules.

If your site comes back online, you know the problem is related to the .htaccess file. Now put the original file back—the issue will be back, but we are now going to fix it.

Fine Tune via Helper Plugin

WP Rocket uses 7 PHP filters to add 7 blocks of rules to your .htaccess file (see reference at the end of this article).

In order to be able to debug those blocks one by one, install this little helper plugin:

📥  Download (.zip):  WP Rocket | Remove All .htaccess Rules
Developers: you can find the code for this plugin on GitHub.

When you have activated the plugin and reloaded your page in the browser, the error 500 should be gone, but now you have removed all the rule blocks of WP Rocket from your .htaccess file.

However, you should remove only those blocks necessary for the error to stay away.
So let’s do this:

1
Remove the add_filter() lines from the plugin, one by one.
2
After each removal, save the file, de-activate and re-activate the helper plugin, and check your site.
3
When the Error 500 comes back, you know the line you just removed was the one making the error stay away.
4
Re-add that lastly removed line and remove all other lines beginning with add_filter.

Voilà, that error 500 should be fixed now!

Note: An alternate method of debugging would be to open your .htaccess file and remove each block of rules one by one until the error goes away. That way you would also know which block causes the problem, but you would still have to the helper plugin in order to permanently solve the issue.

Reference: .htaccess Rules added by WP Rocket

Charset

rocket_htaccess_charset();

# Use UTF-8 encoding for anything served text/plain or text/html
AddDefaultCharset UTF-8
# Force UTF-8 for a number of file formats
<IfModule mod_mime.c>
AddCharset UTF-8 .atom .css .js .json .rss .vtt .xml
</IfModule>

ETag

rocket_htaccess_etag();

# FileETag None is not enough for every server.
<IfModule mod_headers.c>
Header unset ETag
</IfModule>


# Since we’re sending far-future expires, we don’t need ETags for static content.
# developer.yahoo.com/performance/rules.html#etags
FileETag None

WebFonts

rocket_htaccess_web_fonts_access();

# Send CORS headers if browsers request them; enabled by default for images.
<IfModule mod_setenvif.c>
<IfModule mod_headers.c>
# mod_headers, y u no match by Content-Type?!
<FilesMatch "\.(cur|gif|png|jpe?g|svgz?|ico|webp)$">
SetEnvIf Origin ":" IS_CORS
Header set Access-Control-Allow-Origin "*" env=IS_CORS
</FilesMatch>
</IfModule>
</IfModule>


# Allow access to web fonts from all domains.
<FilesMatch "\.(eot|otf|tt[cf]|woff2?)$">
<IfModule mod_headers.c>
Header set Access-Control-Allow-Origin "*"
</IfModule>
</FilesMatch>

FilesMatch

rocket_htaccess_files_match();

<IfModule mod_alias.c>
<FilesMatch "\.(html|htm|rtf|rtx|txt|xsd|xsl|xml)$">
<IfModule mod_headers.c>
Header set X-Powered-By "WP Rocket/3.10-alpha1"
Header unset Pragma
Header append Cache-Control "public"
Header unset Last-Modified
</IfModule>
</FilesMatch>


<FilesMatch "\.(css|htc|js|asf|asx|wax|wmv|wmx|avi|bmp|class|divx|doc|docx|eot|exe|gif|gz|gzip|ico|jpg|jpeg|jpe|json|mdb|mid|midi|mov|qt|mp3|m4a|mp4|m4v|mpeg|mpg|mpe|mpp|otf|odb|odc|odf|odg|odp|ods|odt|ogg|pdf|png|pot|pps|ppt|pptx|ra|ram|svg|svgz|swf|tar|tif|tiff|ttf|ttc|wav|wma|wri|xla|xls|xlsx|xlt|xlw|zip)$">
<IfModule mod_headers.c>
Header unset Pragma
Header append Cache-Control "public"
</IfModule>
</FilesMatch>
</IfModule>

ModExpires

rocket_htaccess_mod_expires();

<IfModule mod_mime.c>
    AddType image/avif                                  avif
    AddType image/avif-sequence                         avifs
</IfModule>

# Expires headers (for better cache control)
<IfModule mod_expires.c>
ExpiresActive on


ExpiresDefault                          "access plus 1 month"


# cache.appcache needs re-requests in FF 3.6 (thanks Remy ~Introducing HTML5)
ExpiresByType text/cache-manifest       "access plus 0 seconds"


# Your document html
ExpiresByType text/html                 "access plus 0 seconds"


# Data
ExpiresByType text/xml                  "access plus 0 seconds"
ExpiresByType application/xml           "access plus 0 seconds"
ExpiresByType application/json          "access plus 0 seconds"


# Feed
ExpiresByType application/rss+xml       "access plus 1 hour"
ExpiresByType application/atom+xml      "access plus 1 hour"


# Favicon (cannot be renamed)
ExpiresByType image/x-icon              "access plus 1 week"


# Media: images, video, audio
ExpiresByType image/gif                     "access plus 4 months"
    ExpiresByType image/png                     "access plus 4 months"
    ExpiresByType image/jpeg                    "access plus 4 months"
    ExpiresByType image/webp                    "access plus 4 months"
    ExpiresByType video/ogg                     "access plus 4 months"
    ExpiresByType audio/ogg                     "access plus 4 months"
    ExpiresByType video/mp4                     "access plus 4 months"
    ExpiresByType video/webm                    "access plus 4 months"
    ExpiresByType image/avif                    "access plus 4 months"
    ExpiresByType image/avif-sequence           "access plus 4 months"

# HTC files  (css3pie)
ExpiresByType text/x-component          "access plus 1 month"


# Webfonts
ExpiresByType font/ttf    "access plus 4 months"
ExpiresByType font/otf    "access plus 4 months"
ExpiresByType font/woff   "access plus 4 months"
ExpiresByType font/woff2  "access plus 4 months"
ExpiresByType image/svg+xml    "access plus 4 months"
ExpiresByType application/vnd.ms-fontobject "access plus 1 month"


# CSS and JavaScript
ExpiresByType text/css                  "access plus 1 year"
ExpiresByType application/javascript    "access plus 1 year"


</IfModule>

ModDeflate

rocket_htaccess_mod_deflate();

# Gzip compression
<IfModule mod_deflate.c>
# Active compression
SetOutputFilter DEFLATE
# Force deflate for mangled headers
<IfModule mod_setenvif.c>
<IfModule mod_headers.c>
SetEnvIfNoCase ^(Accept-EncodXng|X-cept-Encoding|X{15}|~{15}|-{15})$ ^((gzip|deflate)\s*,?\s*)+|[X~-]{4,13}$ HAVE_Accept-Encoding
RequestHeader append Accept-Encoding "gzip,deflate" env=HAVE_Accept-Encoding
# Don’t compress images and other uncompressible content
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png|rar|zip|exe|flv|mov|wma|mp3|avi|swf|mp?g|mp4|webm|webp|pdf)$ no-gzip dont-vary
</IfModule>
</IfModule>


# Compress all output labeled with one of the following MIME-types
<IfModule mod_filter.c>
AddOutputFilterByType DEFLATE application/atom+xml \
		                          application/javascript \
		                          application/json \
		                          application/rss+xml \
		                          application/vnd.ms-fontobject \
		                          application/x-font-ttf \
		                          application/xhtml+xml \
		                          application/xml \
		                          font/opentype \
		                          image/svg+xml \
		                          image/x-icon \
		                          text/css \
		                          text/html \
		                          text/plain \
		                          text/x-component \
		                          text/xml
</IfModule>
<IfModule mod_headers.c>
Header append Vary: Accept-Encoding
</IfModule>
</IfModule>

ModRewrite

rocket_htaccess_mod_rewrite();

<IfModule mod_mime.c>
AddType text/html .html_gzip
AddEncoding gzip .html_gzip
</IfModule>
<IfModule mod_setenvif.c>
SetEnvIfNoCase Request_URI \.html_gzip$ no-gzip
</IfModule>

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{HTTPS} on [OR]
RewriteCond %{SERVER_PORT} ^443$ [OR]
RewriteCond %{HTTP:X-Forwarded-Proto} https
RewriteRule .* - [E=WPR_SSL:-https]
RewriteCond %{HTTP:Accept-Encoding} gzip
RewriteRule .* - [E=WPR_ENC:_gzip]
RewriteCond %{REQUEST_METHOD} GET
RewriteCond %{QUERY_STRING} =""
RewriteCond %{HTTP:Cookie} !(wordpress_logged_in_|wp-postpass_|wptouch_switch_toggle|comment_author_|comment_author_email_) [NC]
RewriteCond %{REQUEST_URI} !^(/_test/|/wp-json/(.*))$ [NC]
RewriteCond %{HTTP_USER_AGENT} !^(facebookexternalhit).* [NC]
RewriteCond "%{DOCUMENT_ROOT}/wp-content/cache/wp-rocket/%{HTTP_HOST}%{REQUEST_URI}/index%{ENV:WPR_SSL}.html%{ENV:WPR_ENC}" -f
RewriteRule .* "/wp-content/cache/wp-rocket/%{HTTP_HOST}%{REQUEST_URI}/index%{ENV:WPR_SSL}.html%{ENV:WPR_ENC}" [L]
</IfModule>

Increasing Memory Limit

If you are experiencing 500 Error and removing htaccess rules doesn't help, you should try to  Increase Memory limit of your server.

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