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snowseo-beacon.php is a single file with no dependencies. It loads before your application, decides in a few microseconds whether the request is worth reporting, and gets out of the way. Your application code is not touched. Requires PHP 7.4 or later.
On WordPress, use the SnowSEO plugin instead. It does the same job and adds settings, buffering and a page-cache coverage check.

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Setup

1

Put the file on your server

Download snowseo-beacon.php and place it somewhere outside your web root:
2

Load it for every request

Add one line to php.ini, your PHP-FPM pool config, or a .htaccess:
php.ini
.htaccess
Then reload PHP-FPM or Apache.
3

Set your site key

Or, if setting environment variables is awkward, define it in a file loaded before the prepend:
Generate the key under Settings → Integrations → Beacon in the SnowSEO dashboard.
Verify with a crawler user agent:

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Configuration

All optional, read from a constant first and then the environment. Default exclusions: /wp-admin, /wp-json, /wp-login.php, /xmlrpc.php, /api/, /graphql, /_next/, /assets/, /static/, /build/, /health, /healthz, /status, /favicon.ico, /robots.txt. Setting SNOWSEO_BEACON_EXCLUDE replaces that list rather than adding to it.

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What it does per request

  1. Exits immediately for CLI, non-GET/HEAD requests, and anything from a browser. This is the overwhelming majority of traffic and it costs a handful of array lookups.
  2. For a request that asked for Markdown or carried no Sec-Fetch-* header, checks the path is a page route and not excluded.
  3. Registers a shutdown function, so nothing happens until your response is already produced.
  4. Calls fastcgi_finish_request() where available, so the visitor’s connection is closed before the report is sent. On PHP-FPM and LiteSpeed this means zero added latency.
  5. POSTs the hit with a 2-second timeout, swallowing every error.
A SnowSEO outage cannot slow or break your site. The worst case is one 2-second timeout on a crawler’s request, after that crawler already has its response.

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High-traffic sites

The standalone client sends one request per reportable hit, because plain PHP has nowhere to keep a buffer between requests. Since ordinary visitor traffic is filtered out before this point, that is crawler-only volume and fine for almost every site. Above roughly ten crawler hits per second you will want batching. Either front the site with a Node runtime and use @snowseo/beacon, or get in touch about the APCu-buffered variant.