Is combine_heads enabled by default?

No. combine_heads is not in CoreFilters, the default RewriteLevel; it runs only when you enable it by name with EnableFilters.

How do I enable combine_heads on Apache and nginx?

Add ModPagespeedEnableFilters combine_heads on Apache or pagespeed EnableFilters combine_heads; on nginx. On IIS, add pagespeed EnableFilters combine_heads to pagespeed.config.

filter · HTML filters

Combine heads (combine_heads)

Q: What does the combine_heads filter do?

combine_heads folds extra elements into the first one. When the module's HTML parse closes a second or later , the contents of that element move into the first head and the emptied element disappears, so the served document carries exactly one head with everything in it. Not a core filter; enable it by name.

Category:: HTML
CoreFilters:: No
OptimizeForBandwidth:: No
Risk:: Generally safe

combine_heads folds extra <head> elements into the first one. When the module’s HTML parse closes a second or later <head>, the contents of that element move into the first head and the emptied element disappears, so the served document carries exactly one head with everything in it. Not a core filter; enable it by name.

How it works

Live demo: combine_heads.

When it helps and when it does not

It helps on pages assembled from fragments that each ship a complete document skeleton: server-side includes that embed whole HTML files, portal or search pages that splice in results blocks with their own <head>, scraped or migrated content pasted with its original head. A browser’s own parser discards the stray <head> tags and keeps the content, so such pages mostly render by accident; the merged output is predictable and gives the module’s head-injecting filters one place to work. On a normal page with a single head the filter changes nothing.

How it decides

The first <head> in the document is the survivor. Each later </head> moves its children into that first head, in document order. The merge cannot cross a flush boundary: when the server streams the page in chunks, heads that close in a later chunk than the first head stay as they are, because content already flushed to the browser cannot be restructured. The filter shares its implementation with add_head: the same pass that inserts a missing <head> performs the merge, so enabling combine_heads also brings add_head’s behavior of inserting a head into documents that have none.

When to use it

Not in CoreFilters: it runs only when you enable it by name.
Risk rating on these docs: Generally safe.

Risks

Content ordering inside the merged head follows the fragments, not any intent the fragments had; a fragment whose styles or scripts assumed their original position relative to other elements should be checked after enabling.
Verify with the X-Mod-Pagespeed response header and a ?PageSpeedFilters=-combine_heads comparison; Is it working? has the steps.

Configuration

Enable it in the module configuration, at server, virtual-host or location scope:

Apache

ModPagespeedEnableFilters combine_heads

nginx

pagespeed EnableFilters combine_heads;

IIS (pagespeed.config)

pagespeed EnableFilters combine_heads

<!-- before: two fragments, each contributing its own head -->
<head>
  <title>Report</title>
</head>
...the first fragment's content...
<head>
  <link rel="stylesheet" href="/css/part2.css" />
</head>
...the second fragment's content...

<!-- after: one head, both fragments' head content in it -->
<head>
  <title>Report</title>
  <link rel="stylesheet" href="/css/part2.css" />
</head>
...the first fragment's content... ...the second fragment's content...

Scoping, ForbidFilters and the thresholds filters read: Choosing filters .

Live example

Merges multiple <head> elements into one.

Measured on the demo page, original against optimized:

HTML size

232 B → 219 B −6%

See the before and after, with the source diff →

Frequently asked questions

What does the combine_heads filter do?: combine_heads folds extra <head> elements into the first one. When the module's HTML parse closes a second or later <head>, the contents of that element move into the first head and the emptied element disappears, so the served document carries exactly one head with everything in it. Not a core filter; enable it by name.
Is combine_heads enabled by default?: No. combine_heads is not in CoreFilters, the default RewriteLevel; it runs only when you enable it by name with EnableFilters.
How do I enable combine_heads on Apache and nginx?: Add ModPagespeedEnableFilters combine_heads on Apache or pagespeed EnableFilters combine_heads; on nginx. On IIS, add pagespeed EnableFilters combine_heads to pagespeed.config.

add_base_tag — Add base tag
add_head — Add head
add_ids — Add IDs
add_instrumentation — Add instrumentation
collapse_whitespace — Collapse whitespace
compute_statistics — Compute HTML statistics
convert_meta_tags — Convert meta tags
debug — Debug comments

This page is drawn from the combine_heads entry on HTML filters. Every filter in one table: PageSpeed filters.