Steady Speed

A WordPress plugin that makes pages load faster without breaking them. It minifies CSS and JavaScript, removes render-blocking files, defers scripts in their original order and lazy-loads images.

It is meant as a safer alternative to Autoptimize-style optimizers. The order in which styles and scripts run is what usually breaks sites, so Steady Speed never changes it. It only optimizes files; for page caching, use your host's cache or any page cache plugin alongside it.

Features

Styles (CSS)

• Minifies stylesheets and rewrites the paths inside them (images, fonts, @import), so they work from any location.
• Puts small stylesheets straight into the page, so they no longer block the first paint.
• Combines only neighbouring stylesheets, so the cascade stays exactly the same. An external @import starts a new file.
• Minifies the large inline style block that block themes print on every page.
• Adds font-display: swap where a theme left it out.
• Optional: loads stylesheets without blocking, together with critical CSS.

Scripts (JavaScript)

• Defers scripts in their original order, inline scripts too. jQuery code, wp_localize_script data and before/after inline scripts keep working.
• Some scripts must run while the page loads: document.write scripts, scripts you exclude, and everything before them. These stay in place.
• Scripts that look up their own address (webpack chunks, document.currentScript) are never moved.
• Minifies unminified files. Code the minifier is not safe with is left as is.
• Optional: combines neighbouring scripts, and loads chat widgets or analytics on the visitor's first interaction.

Images, fonts, HTML

• Lazy-loads images and iframes below the first few.
• Marks the main image with fetchpriority="high" when the theme did not.
• Speeds up Google Fonts, adds preconnects, preloads fonts.
• Removes the emoji script. HTML minification is optional.

Safety

• Test mode: only administrators see optimized pages.
• Add ?nooptimize=1 to any address to see the original page. The admin bar has a link for it.
• On any error, the original page is served. Huge pages and inline scripts are handled without regular-expression limits.
• Clearing keeps old files for a day, so pages saved by a page cache keep working. Common page caches are cleared too.
• Warns when another plugin (Autoptimize, WP Rocket, LiteSpeed Cache and others) optimizes the same files.
• Never touches page-builder editors, AMP, feeds, REST, sitemaps, logins, AJAX or POST requests.
• No external services, accounts or tracking.

Languages: English, Russian, Ukrainian, Hungarian, German. A .pot file is included for other languages.

Requirements

WordPress 6.4+ and PHP 7.4+ (tested up to PHP 8.4 and WordPress 7.1).

Installation

1. Download the latest zip from Releases, or build it yourself (see below).
2. In WordPress, go to Plugins → Add New → Upload Plugin and upload the zip.
3. Activate the plugin. Then open your site in a private window and check that it looks and works as before.
4. Fine-tune the plugin in Settings → Steady Speed.

Development

bin/build.sh                    # builds dist/steady-speed-<version>.zip (git archive, without tests/tools)
python3 tools/i18n/extract.py   # collects translatable strings
python3 tools/i18n/build.py     # writes languages/*.po, *.mo and steady-speed.pot (checks placeholders)

The tests run inside a WordPress install. The authors use WordPress Playground on port 9400.

1. Copy tests/fixtures/ss-helper.php to wp-content/mu-plugins/. It is a test helper; never use it on a live site.
2. Install tests/fixtures/ss-fixture and tests/fixtures/ss-traps as plugins.
3. Run the suites:

• tests/unit.php — 91 unit tests. Run them with ?ss_helper=php&v=require WP_PLUGIN_DIR."/steady-speed/tests/unit.php";.
• tests/e2e/*.py — browser comparisons with Playwright and Chromium. They load each page with and without optimization and compare the results:
  • script order, computed styles and screenshots;
  • a settings matrix;
  • request types;
  • security checks;
  • trap scenarios;
  • theme and plugin compatibility.
• tests/minifier/ — CSS torture test. Computed styles must match in Chromium.

Third-party code

Minify and PathConverter by Matthias Mullie, MIT license. They are bundled under the SteadySpeed\Vendor namespace with one fix: true.valueOf no longer becomes invalid code.

License

GPL-2.0-or-later. See LICENSE.