---
title: "Rank Math’s llms.txt is slow: why and how to fix it"
description: "Rank Math construye el llms.txt en cada visita ejecutando los shortcodes de todas las entradas para sacar un extracto de dos líneas, y con un maquetador de por medio eso son segundos. Te contamos cómo sacarlo de PHP y servirlo como fichero estático."
url: https://artprojectgroup.com/rank-math-llms-txt-slow-why-and-how-to-fix-it
date: 2026-09-21
modified: 2026-09-21
author: "Art Project Group"
image: https://artprojectgroup.com/wp-content/uploads/2023/02/programacion-web-blog.webp
categories: ["Tutorials"]
tags: ["functions.php", "llms.txt", "PHP", "Rank Math SEO", "Web programming"]
type: post
lang: en-US
---

# Rank Math’s llms.txt is slow: why and how to fix it

A few days ago, going over the *Lighthouse* report of one of the sites we maintain, we found that **Rank Math SEO**‘s `llms.txt` file was not even getting read.

The warning is terse, "llms.txt does not follow the recommendations", and underneath it is the real cause, because the request times out before receiving anything.

There is nothing wrong with the file, it simply does not arrive in time, and the reason lies in how the plugin generates it.

### Why is Rank Math’s llms.txt slow?

The `llms` module does not write any file: it registers a rewrite rule on `init`, serves the request on `template_redirect` and builds the whole document on every visit.

The cost is in `add_post_types_data()`, inside `includes/modules/llms/class-llms-txt.php`, which for each entry in the listing runs a `do_shortcode()` over the complete content before asking `Helper::replace_vars()` for the excerpt.

Put another way, to get a two-line description out it renders the entire entry.

If you use a page builder, and here we use *Avada*, each entry is dozens of nested shortcodes that really do run, one after another, multiplied by the number of entries you have in the listing.

In our case, 283 lines of file and 66 KB of output.

### The numbers

Each measurement with its setup, because otherwise the numbers mean nothing:

| Setup | Time |
| --- | --- |
| Dynamic generation, with no cache | ~7 s |
| Cold transient, first request after purging | 1,544 ms |
| Warm transient, with a full WordPress boot | 345-417 ms |
| Static file on disk, served by the server | 26 ms |

What really changes things is getting out of PHP, because the transient only cuts half the journey and leaves the full WordPress boot in the middle.

### The second factor, which is harder to see

Caching the response looks like enough, but it is not, and the reason is not in **Rank Math**.

Check the headers of your own file with `curl -sI https://dominio.ext/llms.txt` and see whether `vary: Accept-Encoding,User-Agent` shows up.

If your server adds `Vary: User-Agent`, and in our case it is added by the `.htaccess` itself from *Avada*‘s compression block, the page cache keeps one copy for each agent family.

Your home page has the mobile copy always warm because it gets visits, but the `llms.txt` gets none, so when PageSpeed asks for it with the agent of a Moto G it lands on an empty copy, and what it finds is a cache miss, a full WordPress boot and, on top of that, the network and processor throttling that Lighthouse applies on mobile.

That is where the request timeout comes from.

A low-traffic route with `Vary: User-Agent` is doomed to always be served cold, and this applies to any PHP-generated route that gets no visits, whether feeds, exports or the entry points you have built yourself.

### Down to work

The way out is to stop generating the document on every visit and to write it just once in the root, since the `!-f` condition of WordPress’s rewrite rule makes the server deliver the file straight from disk without going through PHP.

Specifically we have added this small piece of PHP code to the `functions.php` file of our child theme:

Copy to clipboardSyntax Highlighter// Captures the Rank Math buffer just before the llms.txt is emitted.
add_action(
'rank_math/llms_txt/before_output',
function () {
ob_start();
}
);

// When it finishes, saves a static copy to ABSPATH/llms.txt (atomic write).
add_action(
'rank_math/llms_txt/after_output',
function () {
$content = ob_get_contents();
ob_end_flush();

if ( ! is_string( $content ) || false === strpos( $content, "\n# " ) ) {
return;
}

$file = trailingslashit( ABSPATH ) . 'llms.txt';
$tmp = $file . '.tmp';

if ( false !== file_put_contents( $tmp, $content, LOCK_EX ) ) {
chmod( $tmp, 0644 );
rename( $tmp, $file );
}
}
);

/**
* Schedules the deferred regeneration of the llms.txt (5 min).
*/
function apg_llms_txt_rebuild_schedule() {
if ( ! wp_next_scheduled( 'apg_llms_txt_rebuild' ) ) {
wp_schedule_single_event( time() + 300, 'apg_llms_txt_rebuild' );
}
}

// When the event fires, hits the Rank Math endpoint with a GET to regenerate it.
add_action(
'apg_llms_txt_rebuild',
function () {
wp_remote_get(
home_url( '/index.php?llms_txt=1' ),
[
'timeout' => 60,
'blocking' => false,
'sslverify' => false,
]
);
}
);

// Reschedule when the content changes.
add_action(
'save_post',
function ( $post_id ) {
if ( wp_is_post_revision( $post_id ) || wp_is_post_autosave( $post_id ) ) {
return;
}
apg_llms_txt_rebuild_schedule();
}
);

foreach ( [ 'deleted_post', 'edited_term', 'created_term', 'delete_term', 'update_option_rank-math-options-general' ] as $hook ) {
add_action( $hook, 'apg_llms_txt_rebuild_schedule' );
}Thanks to it **Rank Math** carries on building the document as always, but the output is captured with `ob_start()` on `rank_math/llms_txt/before_output` and dumped to `ABSPATH . 'llms.txt'` on `rank_math/llms_txt/after_output`, which is the moment when the content is already complete.

The write is atomic, because the text goes first to a `.tmp` file and only when it is whole does a `rename()` put it in its place, so no visitor ever sees the route half written.

Checking that the output contains a section header is the safety net, so as not to leave a truncated file on disk if something goes wrong ahead of time.

The regeneration is scheduled with `wp_schedule_single_event()` every time an entry, a term or the plugin’s general options change, with a margin of 300 seconds that groups bursts of saving into a single pass.

And the `apg_llms_txt_rebuild` event does not rebuild anything on its own, it asks for `index.php?llms_txt=1` without blocking the request, lets **Rank Math** generate the document and the same hook as before dumps it to disk again.

It has been running for months on the **APG** site without a single incident.

### The cache of the .txt files

There is one detail worth looking at before calling this closed, and it is in the `.htaccess`.

The site’s cache block marks the `.txt` files with `Cache-Control: max-age=2592000, public` and also gives them an `Expires` of a month, so the freshly regenerated `llms.txt` can carry on being served in its old version long after it has been rewritten.

That does not affect your server —which always delivers the file that is on disk—, but it does affect whatever CDN you have in front and the visitor’s browser, which are not going to ask for it again for thirty days.

If you are in a hurry for the changes to show, take the `txt` extension out of that rule or lower its `max-age`, and if you are not in a hurry, leave it as it is, because an `llms.txt` a couple of days behind does nobody any harm.

### Conclusion

Thanks to this small piece of code the `llms.txt` goes from the long seven seconds of dynamic generation to the 26 milliseconds of a file served from disk, and the *Lighthouse* warning disappears.

The underlying fix, in any case, ought to come from **Rank Math**, using the stored excerpt when it exists instead of rendering the whole entry to build a two-line summary.

We hope you find this little tutorial useful and we look forward to your comments and contributions.