Speculatr for Craft CMS

Installation

Requirements

  • Craft CMS 5.3 or later
  • PHP 8.2 or later

No build step, no runtime dependencies beyond Craft's own, no database tables, and no outbound HTTP requests. Speculatr never talks to anything.

Install

composer require justinholtweb/craft-speculatr
php craft plugin/install speculatr

Or find Speculatr in the Plugin Store and install it there.

What happens immediately

From the moment it is installed, every front-end HTML response carries a small <script type="speculationrules"> block, and signed-out visitors get prerendering at moderate eagerness — the browser starts loading the next page after about 200 ms of hovering a link, which is roughly the point at which somebody has decided to click it.

Nothing else changes. In particular:

  • Signed-in visitors get nothing until you turn them on. A prerender runs a page's JavaScript, and a page rendered for one specific person is the page most likely to be expensive.
  • Nothing you would regret opening early is in scope. The control panel, action requests, every sign-in and sign-out path, and any URL carrying a preview, site or CSRF token are excluded before you have to think about it — read out of your Craft configuration, so a renamed control panel or a custom logout path is covered without anybody remembering.

Check it worked

Open any front-end page and view source. Just before </body> you should find something like:

<script type="speculationrules">
{"prerender":[{"source":"document","where":{"and":[
  {"href_matches":"/*","relative_to":"document"},
  {"not":{"href_matches":"/admin","relative_to":"document"}},
  …
]},"eagerness":"moderate"}]}
</script>

Or from the command line:

php craft speculatr/rules/show

In the control panel, Speculatr → Rules shows the same document, every exclusion with the reason it exists, and a box you can paste a URL into to find out what would happen to a link pointing at it.

Editions

None. Speculatr is free — no editions, no licence key, and no licensing code in the plugin.

Where it works

Chromium browsers — Chrome, Edge, Opera and Android's browsers — from version 121.

Safari and Firefox ignore the rules entirely. That costs their visitors nothing but the couple of kilobytes of JSON, and there is nothing to fall back to: a browser that does not speculate simply loads the page when the reader clicks, exactly as it does today.

Chrome also declines to speculate under Data Saver, on a low battery, when memory is short, or when the reader has turned preloading off in their settings. This is a feature that quietly does nothing when doing something would be rude, which is the right shape for it.

Removing it

php craft plugin/uninstall speculatr

Your pages go back to exactly what they were. Speculatr stores nothing — no tables, no rows — so there is nothing left behind and nothing to clean up.