API session replay is a sophisticated technique used in antidetect browsers and automation frameworks to capture, store, and recreate entire browsing sessions including all authentication states, cookies, local storage, session storage, and API interactions. 

This capability enables seamless resumption of browsing sessions across different devices, browser profiles, or team members while maintaining perfect consistency that prevents platform detection.

When you browse websites, your browser maintains complex session state—authentication tokens, session cookies, cached API responses, local storage data, IndexedDB contents, and more. 

This state determines what you can access, what content appears, and how platforms identify you. Session replay technology captures this entire state ecosystem, stores it securely, and can recreate it precisely in different contexts, making it appear that the same user on the same device is continuing their session.

This technology has become crucial for multi-account management, team collaboration on shared accounts, account handoff between operators, testing and debugging complex web applications, and maintaining operational continuity when switching between devices or browsers.

In the context of antidetect browsers like Multilogin, session replay enables multiple team members to access the same browser profile while maintaining consistent browser fingerprints and session states that platforms cannot distinguish from a single user’s continuous activity.

How API Session Replay Works

Understanding the technical mechanisms helps you leverage this capability effectively.

Session State Capture

Comprehensive session capture involves multiple browser storage mechanisms:

• HTTP Cookies: The foundation of web session management. Session replay captures all cookies including their names, values, domains, paths, expiration times, secure flags, HttpOnly flags, and SameSite attributes. This complete cookie state must be preserved precisely to maintain authentication and session continuity.
• Local Storage: Websites store persistent data in browser local storage using key-value pairs. Modern web applications rely heavily on local storage for user preferences, cached data, and application state. Session replay captures entire local storage contents for each domain visited during the session.
• Session Storage: Similar to local storage but specific to the current browsing session, session storage contents typically don’t survive browser closure. Session replay must capture this temporary state to maintain application functionality when replaying sessions.
• IndexedDB: Complex web applications use IndexedDB for storing large amounts of structured data. Session replay systems capture complete IndexedDB database states including all object stores, indexes, and data records.
• Service Worker State: Progressive web applications register service workers that can intercept network requests and manage offline functionality. Session replay captures service worker registrations and their associated cache storage.
• Authentication Tokens: OAuth tokens, JWT tokens, API keys, and other authentication credentials embedded in various storage mechanisms must be captured carefully to maintain access to protected resources.

Session Storage Format

Captured session data requires structured storage:

• Serialization: Complex browser state objects must be serialized into storable formats, typically JSON or binary formats, preserving all data types, nested structures, and special values like dates or binary data.
• Encryption: Session data often contains sensitive information—authentication tokens, personal data, financial information. Strong encryption protects stored sessions from unauthorized access.
• Compression: Session states can be large, especially for data-heavy applications. Compression reduces storage requirements and transmission times when syncing sessions across devices or team members.
• Versioning: As browsers and websites evolve, session formats may need updates. Version tracking ensures replayed sessions maintain compatibility despite platform changes.
• Metadata Tracking: Alongside session data, systems store metadata—capture timestamp, associated user/profile, capture context, expiration times, and usage statistics.

Session Replay Mechanism

Recreating captured sessions involves precise state restoration:

• Browser Context Initialization: Before replaying session data, the browser must be in the appropriate state—correct device fingerprint, proper screen resolution, accurate timezone, and all other environmental factors matching the original session context.
• Storage Restoration: The replay system injects captured data back into browser storage mechanisms in the correct order. Cookies must be set with proper attributes, local storage repopulated, IndexedDB reconstructed, and service workers reregistered.
• API State Synchronization: Some applications maintain server-side session state. Replay systems may need to synchronize with backend APIs to ensure server state matches restored browser state.
• Validation Checks: After restoration, validation processes confirm session replay succeeded—authentication status verified, expected data accessible, application state consistent with capture point.
• Continuous Sync: For cloud-based profiles used by multiple team members, sessions synchronize continuously. Changes made by one user automatically update stored session state for others accessing the same profile.