Klaviyo custom properties store extra customer data beyond default fields like name or email. For e-commerce brands, they’re essential for personalisation and segmentation, capturing details like style preference, loyalty tier, or favourite category. Unlike built-in fields, they’re fully customisable to fit your needs.

Segmented campaigns can boost email revenue by 760%, far outperforming generic messaging. With custom properties, you can send VIPs exclusive offers or tailor product recommendations based on size preference. Want to refine your segmentation strategy further? Check out our guide on 3 Klaviyo Segmentation Strategies to Boost DTC Sales for actionable tactics.

This guide covers setting up custom properties (manually, via forms, CSV imports, or API), using them for segmentation and automation, and troubleshooting common issues. We’ll also explore advanced use cases like dynamic content, conditional flows, and developer integrations. By the end, you’ll know how to leverage custom properties to maximise your email and SMS marketing success.

What Are Klaviyo Custom Properties?

Klaviyo custom properties are extra profile fields that you define, appearing under “Custom Properties” in a customer’s profile. Unlike Klaviyo’s default fields (Email, Name, Phone), these are fully customisable, letting you store data relevant to your brand.

Think of them as tags or labels that personalise your marketing. A fashion store might track Size Preference, a beauty brand could store Skin Type, and a loyalty program may use Loyalty Tier (Silver, Gold, VIP). These properties help segment customers, personalise emails/SMS, and automate flows based on specific attributes.

For example, you could:

• Send product recommendations tailored to a shopper’s size.

• Offer exclusive rewards to VIP members.

• Create segmented flows, like branching a welcome series based on a customer’s Interest (Men’s vs. Women’s Fashion).

By capturing key data points, you gain a 360° view of each customer—allowing for smarter segmentation, automation, and personalisation in Klaviyo.

Source: Klaviyo 

Common Custom Properties

Every business will have different custom properties based on their needs. Here are some common examples of e-commerce and how they can be used:

Source: Klaviyo 

How to Add and Manage Custom Properties in Klaviyo

Creating and managing custom properties in Klaviyo is straightforward. You can add them in several ways depending on your workflow:

Methods to Add Custom Properties:

1. Manually via Profile Editing

• Go to Profiles, select a contact, and scroll to Custom Properties.

• Click “Add custom property,” enter a Property Name (e.g. “Loyalty Tier”), and assign a Value (e.g. “Gold”).

• Best for one-off updates or testing. Be consistent with naming to avoid duplicates.

  
  

2. Through Signup Forms & Preference Pages

• Use forms to collect zero-party data (e.g. “What’s your favourite product category?”).

• Klaviyo automatically stores responses as custom properties.

• Preference centres allow customers to update interests or birthdays, keeping data fresh.

  
  

3. Bulk Import via CSV

• Upload customer data from another ESP, CRM, or spreadsheet.

• Prepare a CSV with Email (or unique ID) and custom properties.

• Go to Lists & Segments > Manage List > Import Contacts > Upload & Map Fields.

• Klaviyo creates new custom properties automatically if they don’t exist.

  
  

4. Using Klaviyo’s API

• Automate updates using the Identify API via a POST request.

• Best for real-time syncing—e.g. update “Points Balance” in Klaviyo when a customer earns loyalty points in Shopify. For a deeper dive into syncing Klaviyo with external tools, read our step-by-step Klaviyo x Shopify Integration Guide.

• Klaviyo also pulls custom data from native integrations (e.g. “Review Rating” from review apps).

• Ideal for brands with developer resources to ensure always-accurate properties.

  
  

Best Practices for Data Management:

Once you start adding custom properties, it’s important to manage them well so your data stays clean and useful.

1. Keep Naming Consistent

Klaviyo is case-sensitive, so “VIPStatus” ≠ “vipstatus”—this can create duplicates. Stick to a clear format like “VIP Status” or “vip_status”. Avoid spaces and special characters to prevent errors in code and templates. 

2. Automate Updates

Reduce manual work by using Klaviyo Flows to update properties dynamically. For example:

• After a purchase, update “Last Purchase Date” automatically.

• Set “Repeat Customer” = True when someone places their second order.
  Leverage integrations (e.g. loyalty apps) to sync data in real time instead of manual edits.

3. Keep Data Fresh

Regularly audit and remove outdated properties. If you collected "Interested in Product X" two years ago but no longer sell it, phase it out via CSV updates. Ensure new subscribers receive relevant property updates (e.g. “Sign-up Date”).

4. Avoid Over-Segmentation

Don't create overly specific micro-segments (e.g. "Females in UK, VIP tier, interested in Shoes, bought in last 30 days"). Focus on high-impact segmentation, like grouping all VIPs for targeted offers. Stick to properties that are actively used—it’s better to maintain 5 relevant ones than clutter profiles with 50 unused fields.

By following these practices – consistent naming, automation, data hygiene, and strategic segmentation – you’ll ensure your custom properties remain a reliable asset rather than a source of chaos.

How to Use Custom Properties for Segmentation & Personalisation

Now that your custom properties are set up, let’s put them to work! The real power of custom properties is in segmentation and personalisation. They allow you to group customers by very specific criteria and tailor your messages accordingly.

Creating Segments Based on Custom Properties:

In Klaviyo’s segment builder, you can create dynamic groups based on custom properties. Select "Properties about someone", then choose the property and value to filter profiles. If a new property isn’t appearing, ensure at least one profile has that value set.

Example Segments:

• VIP Customers: Segment by Loyalty Tier = Gold or Total Spend > £500 to target high-value buyers with exclusive perks. Want to maximise repeat purchases? Our Winback Flow Guide explains how to re-engage lapsed customers with personalised messaging.

• Product Interests: Use properties like "Favourite Category = Skincare" to send targeted content.

• Lifecycle Stages: Define "Customer Stage" (New, Active, Lapsed) and create automated win-back or onboarding flows.

Personalising Emails & SMS with Custom Properties

Klaviyo’s template tags allow inserting custom property values into messages.

Example:

 📧 Email: "We hope you’re enjoying your {{ person|lookup:'First Purchase Product' }}!"
📱 SMS: "Hi {{ first_name }}, thanks for being a loyal {{ vip_status }} member!"

Use conditional content to show different messages based on stored properties.
Example:

This ensures each customer sees tailored content, improving engagement.

Advanced Use Cases

• Conditional Splits in Flows: Use custom properties to personalise automation. Example: VIPs get a bigger discount in an abandoned cart flow, while regular customers receive a standard reminder

•  Dynamic Product Recommendations: Use stored preferences to populate emails/SMS with personalised product suggestions.

•  Multi-Channel Retargeting: Sync Klaviyo segments (built using custom properties) to Facebook & Google Ads for more personalised retargeting. Learn how to integrate Klaviyo with Google Ads for more effective audience targeting in our Klaviyo x Google Ads Guide.

API & Developer Integration

For those with technical resources or needing deeper integrations, Klaviyo’s API allows you to automate and extend the use of custom properties even further. Here are two key ways to integrate:

Automating Custom Property Updates via API

To update profile properties in real time, Klaviyo’s Identify API (v1/v2) and Profiles API (v3) allow seamless integration.

1. Use Case: Auto-Tagging Customers

When a user logs in or takes an action, your site can push an Identify call to Klaviyo, setting properties dynamically:

This automatically updates profiles—no manual work needed.

2. Syncing Data from External Systems

If using CRM platforms (Salesforce, HubSpot) or loyalty apps, API calls or Zapier integrations ensure real-time profile updates. This prevents data silos, keeping Klaviyo segments accurate.

Klaviyo’s new APIs support batch updates & error handling—check the Klaviyo Developer Portal for best practices. 

Using Custom Properties in Advanced Workflows

Custom properties can also be used in more advanced workflows and custom development around Klaviyo:

Dynamic Content Personalisation (Liquid Syntax)

• Klaviyo supports Liquid templating, allowing advanced personalisation in emails. You can:
  Loop through stored values (if multiple items are saved in a property).

•  Format properties dynamically (e.g., calculate age from a date of birth).

•  Use if/else logic to customise content based on customer attributes.

While most use basic property lookups, developers can parse JSON or apply complex formatting for even deeper personalisation.

Triggering Flows & Webhooks Based on Custom Properties

• Klaviyo flows can’t trigger directly from property changes, but you can:
  Create a segment (e.g., "Back in Stock Alert = True") and trigger a Segment-Triggered Flow when a profile enters.

•  Use webhooks in flows to update external systems when a property changes.

•  Have an API update trigger a metric event, which then triggers a flow that uses properties for decision-making.

This creates a dynamic, automated feedback loop where flows influence customer data and vice versa.

Shopify Plus Scripts & Google Tag Manager (GTM) Syncing

• Shopify Plus Scripts can tag high-value orders, which can trigger a Klaviyo API update (e.g., set “VIP Buyer = True”)

•  GTM can capture site interactions (e.g., clicking “Show Men’s Products”) and send an identify call to Klaviyo, updating a property (“Site Pref: Mens = True”).

Troubleshooting & Avoiding Common Pitfalls

Custom properties are powerful, but you might run into some hiccups. Here are common issues and how to resolve them:

1. Custom Property Not Showing in Segments

If a property doesn’t appear in the segment builder, it likely doesn’t exist on any profile or has blank values. Add it to a test profile, refresh, and check spelling and case (e.g. "Favorite Color" vs "favorite_color"). Ensure recent CSV imports were successful.

2. Syncing & Updating Issues

API updates can fail due to incorrect formatting, race conditions, or authentication errors. Klaviyo only saves persistent properties via the Identify API, not the Track API (which logs event-based properties). Ensure integrations aren’t overwriting the same property at the same time.

3. Duplicate or Conflicting Properties

Klaviyo treats different cases and spaces as unique properties (e.g. "Gender" vs "gender"). To clean up:

• Export profiles, check for duplicates.

• Standardise one format.

• Re-upload profiles with the correct property.

4. Event vs. Profile Property Clashes

If an event and a profile property share the same name (e.g. "Subscription Status"), Klaviyo may not allow event-based trigger splits. To fix this, rename one (e.g. "Subscription_Status_event") to avoid confusion.

5. Unintended Overwrites

CSV imports don’t erase properties unless explicitly updated. However, accidental data overwrites (e.g. setting all cities to "London") can’t be undone. Always test updates on a small batch of profiles first.

6. Case Sensitivity in Emails

Custom properties in emails/SMS must match exactly. If your property is "Favorite Product", using {{ person|lookup:'favorite product' }} will fail. Always copy and paste property names to avoid errors.

FAQs

1. Can I edit or delete a custom property?

You can’t rename a custom property in Klaviyo. Instead, create a new one and migrate data via CSV import or API, then stop using the old one. To remove a property, clear it from all profiles (e.g. import a CSV with blank values). Klaviyo won’t display unused properties, but periodic clean-ups help reduce clutter.

2. Are custom property names case-sensitive?

Yes—Klaviyo treats "VIPStatus" and "vipstatus" as different properties. Use consistent spelling and casing to avoid duplicates. Values (e.g. "Gold" vs "gold") may also be case-sensitive in segmentation, so standardise formats.

3. Is there a limit on the number of custom properties?

No official limit, but avoid clutter. Too many properties can make segmentation harder. Stick to properties that directly impact marketing efforts—20 or fewer is practical for most brands.

4. Can I use custom properties in flow triggers or filters?

You can’t trigger a flow based on a property change, but you can use them in flow filters and conditional splits. A workaround is to trigger flows based on segments, where custom properties define segments.

5. What happens to custom properties if I delete a profile?

Deleting a profile removes all their custom properties. If they were the only user with a certain property, it will disappear from dropdowns. However, profile deletion is rare outside of GDPR or data cleanup cases.

6. How do I bulk update custom properties?

Use a CSV import:

• Export a list of contacts.

• Add new columns for custom properties and populate values.

• Re-upload and map columns to Klaviyo properties.

Conclusion

Klaviyo custom properties unlock a new level of personalisation, segmentation, and automation, but many brands struggle with inconsistent naming, outdated data, and underutilised segments. Without clean, structured properties, your marketing efforts may be inefficient—sending irrelevant emails, missing high-value customers, or losing engagement.

By implementing clear naming conventions, automated updates, and dynamic content, you can transform your email & SMS marketing into a highly targeted, conversion-driven strategy. 

Fixing messy properties and optimising your setup ensures you’re making the most of your data—without manual headaches.

Key Takeaways

• Custom properties enable deeper personalisation by storing customer-specific data beyond default fields.

• Segmented campaigns boost email revenue by 760%, outperforming generic messaging.

• Add properties manually, via forms, CSV import, or API to keep data up-to-date.

• Use structured naming conventions to prevent duplicates and segmentation issues.

• Automate updates with Klaviyo Flows & API to reduce manual errors.

• Target VIPs and high spenders with segmented offers and exclusive perks.

• Personalise emails & SMS with stored preferences like size, interests, or past purchases.

• Trigger lifecycle-based flows (New, Active, Lapsed customers) for better engagement.

• Leverage conditional splits and dynamic content to customise automation paths.

• Sync Klaviyo segments with Facebook & Google Ads for smarter retargeting.

• Regularly audit data and remove outdated properties to maintain clean segmentation.

• Troubleshoot missing segments by ensuring properties exist on at least one profile.

Are Custom Properties Not Working as Expected?

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