How Pertento uses local storage

Pertento relies on local storage to ensure stable experiment behavior, accurate variant attribution and consistent user experience across sessions. Local storage allows Pertento to keep track of which variants a visitor has been assigned to without using cookies or personal data.

What Pertento stores

Pertento writes a small set of keys to local storage for each website. These keys allow the script to:

• remember which experiments the visitor has seen
• persist variant selection across sessions
• avoid reassigning users to different variants
• support URL-based debugging or variant switching

Common keys include:

• PERTENTO-VISITED-xxxx Indicates that the visitor has been assigned to a specific experiment and variant.
• PERTENTO_UUID A non-personal, random identifier used only for experiment consistency.
• PERTENTO_DEBUG Enables debug mode when activated through developer tools.
• PERTENTO_VARIANTS_URL_SEARCH (LEGACY) Stores experiment and variant overrides .
• PERTENTO_EXP_VAR (CURRENT) Stores experiment and variant overrides .

Values stored in these keys contain no personal data and cannot be used to identify the visitor.

Persistence across sessions

Because Pertento stores variant assignments in local storage, visitors remain in the same variant even if they return days later or move between pages. This prevents attribution drift and ensures cleaner experiment data.

Overriding variants through local storage parameters

Pertento supports variant switching through parameters for testing and QA.

Using the appropriate query string, you can manually load a specific experiment and variant. Pertento stores this override in PERTENTO_EXP_VAR so that navigation or page refreshes keep the visitor in the selected variant.

This functionality is intended for developers, QA teams and internal testing.

No personal data

Local storage values contain only experiment IDs, variant IDs and internal state flags. Pertento does not store personal information, behavioral history or identifiers that can link data across systems.

This means local storage usage does not require user consent and complies with privacy regulations.