For a small ecommerce catalog, the best free or free-tier browse/category optimization tools are usually the ones that let you test:

• category page layouts
• product sorting and filtering
• nav/browse experience
• search-to-category behavior
• clicks, conversion, and engagement

Here are the strongest options, depending on what you mean by “optimization”:

1) Google Optimize alternatives

Google Optimize is discontinued, so the best free replacements are:

• VWO Free / free trial
• Convert.com trial
• Zoho PageSense trial
• GrowthBook (open source + free self-hosted)
• Unbounce Smart Traffic is more landing-page focused, not ideal for category pages

Best pick for testing:

GrowthBook

• Free/open-source option
• Supports feature flags and experimentation
• Good if you have technical support
• Better for small catalogs if you want controlled testing without paying much

2) Search and browse optimization tools with free tiers

These are especially useful if your “category optimization” includes product ranking, filtering, and merchandising:

Algolia

• Has a free tier
• Great for category sorting, filtering, and search relevance
• Strong if your catalog is small and you want fast browse/search improvements

Doofinder

• Often offers trial/free demo options
• Easy to set up
• Good for improving internal search and category navigation

Shopify Search & Discovery (if you’re on Shopify)

• Free
• Good for:
  • collection merchandising
  • filters
  • product recommendations
  • search tuning
• One of the best no-cost options for Shopify stores

Elastic / OpenSearch

• Free if self-hosted, but more technical
• Good for advanced browse/search optimization
• Usually overkill for a small catalog unless you have dev support

3) A/B testing and behavior analytics platforms with free plans

These help you test whether category changes actually improve performance.

Microsoft Clarity

• Free
• Heatmaps, session replays, click behavior
• Great for category page UX diagnosis
• Not a testing platform by itself, but very useful for identifying problems

PostHog

• Free tier available
• Feature flags + experiments + product analytics
• Strong option for small ecommerce catalogs if you want experimentation and analytics in one place

Matomo

• Free self-hosted
• Analytics-focused
• Good for tracking browse behavior, though less direct for testing than PostHog/GrowthBook

4) Merchandising/category testing tools

If your focus is specifically category page merchandising and ranking:

Category merchandising platforms to look at

Most dedicated tools are paid, but some offer trials:

• Searchspring
• Nosto
• Constructor
• Klevu
• Reflektion

For a small catalog, these are often expensive, but trials can help you validate whether you need them.

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Best free choices by scenario

If you use Shopify

Best free stack:

• Shopify Search & Discovery
• Microsoft Clarity
• PostHog or GA4
• Optional: GrowthBook for testing

If you want open-source and flexible

• GrowthBook
• PostHog
• Clarity
• Optional: Algolia for search/browse

If your main pain is category sorting/filtering

• Algolia
• Shopify Search & Discovery
• Doofinder trial

If you want UX insight before changing categories

• Microsoft Clarity
• Hotjar free tier (limited, but useful)

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My short recommendation

For a small ecommerce catalog, the best free setup is usually:

1. Microsoft Clarity for behavior insight
2. PostHog or GrowthBook for experimentation
3. Shopify Search & Discovery or Algolia free tier for browse/category improvements

If you want, I can also give you:

• a ranked top 5 list
• a setup stack for Shopify
• or a comparison table of free tools by feature.