Autoptimize review: the best free file optimization plugin?

Autoptimize is different from other plugins on this list. It's not a cache plugin - it doesn't do page caching. But it is an essential part of WordPress performance optimization.

In this review, I explain what Autoptimize does, why you need it (or not), and how it combines with cache plugins. Spoiler: if you use WP Super Cache, Autoptimize is your best friend.

Focus: file optimization, not caching

Let's be clear right away: Autoptimize is NOT a cache plugin.

What doesn't it do?

• Page caching (storing HTML files)
• Object caching (database queries)
• Browser caching
• CDN integration

What does it do?

Autoptimize focuses on one thing: optimizing your CSS, JavaScript and HTML files.

• CSS aggregation - Combines multiple CSS files
• CSS minification - Reduces CSS by removing unnecessary spaces/comments
• JS aggregation - Combines JavaScript files
• JS minification - Reduces JavaScript
• HTML minification - Reduces HTML
• Image lazy loading - Loads images only when scrolling
• Critical CSS - Loads important CSS inline (Pro)

Why is this important?

A WordPress site often loads:

• 10-20 CSS files
• 15-30 JavaScript files
• Lots of unnecessary code

Autoptimize reduces this to:

• 1-2 CSS files
• 1-2 JS files
• 30-50% smaller files

The result: Faster load times, better PageSpeed scores.

CSS and JS aggregation: fewer HTTP requests

One of the most powerful features: file combining.

The problem:

Each WordPress plugin adds CSS and JS:

• Yoast SEO: 2 CSS, 1 JS
• Contact Form 7: 1 CSS, 2 JS
• WooCommerce: 5 CSS, 8 JS
• Theme: 3 CSS, 4 JS

Total: 11 CSS, 15 JS files. That's 26 HTTP requests just for CSS/JS.

The solution: aggregation

Autoptimize combines everything:

• 11 CSS files → 1 CSS file
• 15 JS files → 1-2 JS files

From 26 requests to 2-3. Huge win.

Note: HTTP/2 makes this less important

With HTTP/1.1, file combining was essential. HTTP/2 can download multiple files in parallel.

But combining still helps because:

• Smaller total file size (through compression)
• Less overhead
• Better PageSpeed score

My advice:

Test with and without combining. For most sites it still helps.

HTML minification: smaller pages

HTML minification reduces your HTML code.

What gets removed?

• HTML comments (<!-- comment -->)
• Unnecessary whitespace
• Line breaks
• Extra spaces

Before and after example:

Before minification:

<!-- Header section -->
<header>
<h1>My Website</h1>
<nav>
<ul>
<li><a href="/">Home</a></li>
</ul>
</nav>
</header>

After minification:

<header><h1>My Website</h1><nav><ul><li><a href="/">Home</a></li></ul></nav></header>

Result:

Typically 5-15% smaller HTML. Not spectacular, but every bit helps.

Is it safe?

Usually yes. But sometimes it breaks:

• Inline JavaScript expecting formatting
• Specific CSS selectors
• Template engines

Always test thoroughly after activation.

Image lazy loading: built-in bonus

Autoptimize has lazy loading built-in - images only load when scrolling.

How does it work?

Normal situation:

• Page loads
• All 30 images are downloaded immediately
• Even those at the bottom that nobody sees

With lazy loading:

• Page loads
• Only visible images download
• When scrolling: new images load

Performance impact:

My test blog article (25 images):

• Without lazy load: 4.2s load time, 8MB download
• With lazy load: 1.8s load time, 2.1MB initial download
• 57% faster

Note: WordPress has this built-in

Since WordPress 5.5, native lazy loading is built-in. Autoptimize's lazy load is an alternative with more options.

My advice:

Use Autoptimize's lazy load if you:

• Want more control (exclude certain images, etc.)
• Want placeholders during loading
• Have compatibility issues with native lazy load

Otherwise: native WordPress lazy load is sufficient.

No page caching: combine with cache plugin

This is crucial to understand: Autoptimize does NOT do page caching.

What does that mean?

Autoptimize optimizes your files, but:

• WordPress still runs on every visit
• Database queries still happen
• PHP processing still happens

You also need a cache plugin.

Perfect combinations:

WP Super Cache + Autoptimize

• WP Super Cache: page caching
• Autoptimize: file optimization
• Together: complete performance solution
• Cost: €0

LiteSpeed Cache + Autoptimize

• Note: LiteSpeed Cache has minification built-in
• Use either LiteSpeed's minification or Autoptimize
• Not both at the same time (conflict)

WP Rocket + Autoptimize

• Not needed! WP Rocket has everything built-in
• Adding Autoptimize causes conflict

W3 Total Cache + Autoptimize

• W3TC also has minification
• Choose one for minification
• I recommend Autoptimize (easier)

Bottom line:

Autoptimize is perfect alongside simple cache plugins (WP Super Cache). With advanced plugins (WP Rocket, LSCache) it's redundant.

Combining with other plugins: what works?

Autoptimize works with most plugins, but there are exceptions.

Works perfect:

• WP Super Cache
• WooCommerce (with correct exclusions)
• Contact Form 7
• Yoast SEO
• Elementor (usually)
• Gravity Forms

Sometimes conflicts:

• WP Rocket (overlap in features)
• LiteSpeed Cache (own minification)
• W3 Total Cache (own minification)
• Async JavaScript plugin (double JS optimization)
• Swift Performance (overlap)

Requires configuration:

• Page builders (Elementor, Divi) - exclude builder CSS/JS
• Sliders (Revolution Slider) - exclude slider JS
• Inline editing plugins - exclude their scripts

How to add exclusions:

Autoptimize > JS, CSS & HTML > Exclude scripts from Autoptimize:

/wp-content/plugins/elementor/
js/jquery/jquery.min.js

Each script on new line.

Completely free (Pro available)

Autoptimize is free, but also has a Pro version.

Free version contains:

• CSS aggregation and minification
• JS aggregation and minification
• HTML minification
• Image lazy loading
• Google Fonts optimization
• Extra optimization options

Pro version (€5/month or €50/year) adds:

• Critical CSS generation (automatic)
• Advanced image optimization
• CDN for optimized files
• Priority support
• Advanced lazy load options

Is Pro worth it?

For most sites: no.

Critical CSS is the killer feature in Pro. It ensures that:

• Above-the-fold CSS loads inline
• Rest of CSS loads async
• Page renders instantly

But you can also generate critical CSS for free:

• Via tools like critical-css.com
• Manually add in theme
• Via free plugins

Who should consider Pro?

• Agencies with many sites (€50/year for unlimited is good)
• Sites where every millisecond counts
• Who doesn't have time for manual critical CSS

For the rest: free version is excellent.

Performance impact: tests and benchmarks

Autoptimize alone doesn't give the full picture (it's not a cache plugin), but here's the difference.

Test 1: WordPress blog + WP Super Cache

Without Autoptimize:

• PageSpeed: 84/100
• Load time: 1.4s
• CSS: 11 files, 180KB
• JS: 15 files, 320KB

With Autoptimize:

• PageSpeed: 91/100
• Load time: 0.9s
• CSS: 1 file, 85KB
• JS: 2 files, 190KB

Improvement: 36% faster, 48% smaller files

Test 2: WooCommerce shop (without cache)

Without Autoptimize:

• PageSpeed: 62/100
• Load time: 4.2s

With Autoptimize (only, no cache!):

• PageSpeed: 71/100
• Load time: 3.1s

Improvement: 26% faster

(Still slow because no page caching)

Test 3: Complete setup (WP Super Cache + Autoptimize)

Clean WordPress:

• PageSpeed: 78/100
• Load time: 1.8s

WP Super Cache only:

• PageSpeed: 88/100
• Load time: 0.9s

WP Super Cache + Autoptimize:

• PageSpeed: 94/100
• Load time: 0.6s

Combination: 67% faster than no optimization

Conclusion:

Autoptimize gives 20-35% extra speed on top of caching. The combination is powerful.

Pros and cons: honest balance

Pros

Free but powerful Pro version exists, but free is already very complete. No forced upsells.

Laser focus on file optimization Does one thing (CSS/JS/HTML optimization) and does it excellently.

Easy to use Simpler than W3 Total Cache. Activate, choose settings, done.

Good defaults Out-of-the-box configuration works for 80% of sites.

Active development Regular updates and new features. Developer responds quickly to issues.

Lazy loading included Bonus feature that adds a lot of value.

Google Fonts optimization Can host Google Fonts locally or load async. Handy for GDPR.

Perfect alongside WP Super Cache Best combo for free complete optimization.

Cons

No page caching You still need a cache plugin. Autoptimize is not complete.

Can break things JS combining can break scripts that expect load order. Requires testing.

Learning curve for exclusions If something breaks, you need to know which files to exclude. Can be frustrating.

Critical CSS costs money Free version has no automatic critical CSS. Pro is €50/year.

Sometimes conflicts with page builders Elementor, Divi can have issues. Requires exclusions.

No object/database caching Focus is files only. Complex sites need more.

Support is basic Free version has forum support. Can take days for answer.

Setup and configuration: for beginners

Autoptimize is relatively simple, but here are the essentials.

Step 1: Installation

1. WordPress > Plugins > Add New
2. Search "Autoptimize"
3. Install and activate
4. Settings > Autoptimize appears

Step 2: Basic configuration

Go to Settings > Autoptimize > JS, CSS & HTML:

JavaScript Options:

• ✅ Optimize JavaScript Code
• ❌ Aggregate JS-files (test first, can break)
• Also optimize for logged in editors: optional

CSS Options:

• ✅ Optimize CSS Code
• ✅ Aggregate CSS-files
• ✅ Generate data: URIs for images
• Also optimize for logged in editors: optional

HTML Options:

• ✅ Optimize HTML Code

Step 3: Extra options

Go to Extra tab:

Google Fonts:

• ✅ Remove Google Fonts (if you don't use Google Fonts)
• Or: Combine and link in (better performance)

Images:

• ✅ Lazy-load images

Step 4: Test thoroughly

1. Clear all caches (Autoptimize + your cache plugin)
2. Check homepage - does everything look good?
3. Test navigation
4. Test forms (contact form!)
5. Test JavaScript functionality (sliders, accordions, etc.)
6. Run PageSpeed Insights

Step 5: Troubleshooting (if needed)

JavaScript broken?

1. Go to JS, CSS & HTML tab
2. Disable "Aggregate JS-files"
3. Clear cache, test again
4. Or: exclude specific scripts

CSS layout broken?

1. Go to JS, CSS & HTML tab
2. Under CSS Options > "Exclude CSS from Autoptimize"
3. Add problematic CSS, e.g:

   /wp-content/themes/your-theme/style.css
   

Exclude specific script:

1. Identify which script causes problems (browser console)
2. Go to JS, CSS & HTML > Exclude scripts from Autoptimize
3. Add, for example:

   elementor
   revolutionslider
   

Step 6: Optimize further (optional)

If everything works:

JS Options:

• ✅ Enable "Aggregate JS-files" again (test well!)
• ⚠️ "Also defer inline JS" - only for experts

CSS Options:

• ✅ "Inline and Defer CSS" - can solve render-blocking CSS
• Test first, can break layout

Pros and cons versus alternatives

Autoptimize vs WP Rocket

Feature	Autoptimize	WP Rocket
Price	Free	€59/year
Page caching	❌	✅
CSS/JS minify	✅	✅
Lazy loading	✅	✅
Critical CSS	€ (Pro)	✅
Database cleanup	❌	✅
Support	Basic	Premium
Ease of use	Medium	Easy

When to choose Autoptimize:

• Budget €0
• You already have a cache plugin (WP Super Cache)
• You only want file optimization

When to choose WP Rocket:

• Budget is not an issue
• You want all-in-one solution
• You want premium support

Autoptimize vs LiteSpeed Cache (with minification)

Feature	Autoptimize	LSCache
Price	Free	Free
CSS/JS minify	✅	✅
Page caching	❌	✅
Image optimization	€ (Pro)	✅ (QUIC.cloud)
Configuration	Medium	Complex

When to choose Autoptimize:

• No LiteSpeed hosting
• Simpler minification

When to choose LSCache:

• LiteSpeed hosting
• You want everything in one plugin

Frequently asked questions

Is Autoptimize a cache plugin?

No! Autoptimize does file optimization (CSS/JS/HTML minification), but no page caching. You also need a cache plugin like WP Super Cache.

Can I combine Autoptimize with WP Rocket?

Not recommended. WP Rocket has minification built-in. Both together causes conflicts and overhead. Choose one.

Why does JavaScript break after activation?

JS aggregation combines all scripts. Some scripts expect specific load order. Disable "Aggregate JS" or exclude problematic scripts.

Autoptimize vs WP Rocket: which is better?

Depends on budget and needs:

• Free + separate cache plugin: Autoptimize + WP Super Cache
• Paid all-in-one: WP Rocket WP Rocket is easier, Autoptimize is free.

How do I generate critical CSS without Pro?

Use tools like:

• criticalcss.com (free tier)
• web.dev/critical-rendering-path Paste generated CSS in theme or via plugin.

Does Autoptimize work with WooCommerce?

Yes, but exclude checkout/cart scripts. Add to exclusions:

wc-
cart
checkout

Is Pro version worth it?

For most sites: no. Critical CSS is handy but can also be free. For agencies with many sites: €50/year unlimited can be worth it.

How do I know if Autoptimize works?

1. View page source
2. Search for "autoptimize" in URLs
3. CSS/JS files have autoptimize in path
4. Run PageSpeed Insights - score should be better