How Sync Works in Browser-Based Apps Like Arc or Vivaldi

 Synchronization—or sync, as it’s often called—is one of the most essential and complex features in modern browsers. It allows users to maintain a consistent browsing experience across multiple devices by ensuring that bookmarks, open tabs, passwords, extensions, settings, and even browsing history remain uniform wherever they sign in.

Browsers like Arc (by The Browser Company) and Vivaldi (by Vivaldi Technologies) take this concept beyond the basics. They integrate synchronization deeply into their ecosystems, prioritizing privacy, customization, and user control—all while maintaining high performance. This guide explores in detail how sync works in browser-based apps like Arc and Vivaldi, how data moves between devices, what privacy safeguards are in place, and what makes their syncing systems distinct from mainstream browsers like Chrome or Edge.

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1. Understanding Browser Sync in General

Before diving into Arc and Vivaldi specifically, it’s useful to understand the fundamentals of browser synchronization. At its core, syncing in a browser works through these steps:

1. User Authentication:
   The user signs in to the browser using an account (e.g., Arc account or Vivaldi account).

2. Data Collection:
   The browser gathers sync-enabled data categories like bookmarks, extensions, history, and settings from the local device.

3. Encryption and Packaging:
   The data is encrypted—either locally on the device (end-to-end encryption) or on the server (server-side encryption)—and prepared for transmission.

4. Upload to Sync Server:
   The encrypted data is sent to the browser’s sync server, where it’s stored temporarily or persistently, depending on the platform.

5. Data Distribution:
   Other devices logged into the same account retrieve the latest encrypted data from the sync server and apply it locally, merging or replacing existing items as needed.

6. Conflict Resolution:
   If two devices modify the same data (for example, renaming a bookmark folder), the browser must determine which change to prioritize—usually using timestamps or last-modified rules.

This entire process happens silently and automatically in the background, ensuring minimal user effort while maintaining consistent data across devices.

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2. How Sync Works in Arc Browser

A. Overview of Arc’s Philosophy

Arc is not just a browser—it’s an attempt to reimagine web navigation and productivity. Its synchronization system reflects this philosophy, focusing on user experience, real-time updates, and seamless continuity between devices.

Arc uses a cloud-based account system linked to Arc accounts, allowing users to sign in and sync their browser environment—spaces, tabs, pinned sites, extensions, and themes—across all installations of Arc.

B. Arc’s Synchronization Components

1. User Account and Authentication

   • Arc users sign in with their Arc account credentials.

   • Authentication uses modern identity protocols like OAuth 2.0 and token-based sessions to ensure secure access.

   • Each device is registered under the user’s profile, allowing Arc to manage which devices are authorized to sync.

2. Data Types Synced
   Arc syncs a wide range of data, including:

   • Bookmarks and folders

   • Spaces and tab groups

   • Workspaces layouts

   • Extensions and settings

   • Passwords (if the user has enabled password sync)

   • Themes and UI customizations

3. End-to-End Encryption (E2EE)
   Arc places strong emphasis on privacy-first design. Sensitive information like passwords and browsing history is encrypted locally before upload.

   • Only the user’s devices can decrypt this data.

   • Arc’s servers can store the encrypted data but cannot read it.

   • This ensures that even Arc’s developers have no access to your sync contents.

4. Sync Server Infrastructure
   Arc uses distributed cloud servers—believed to be hosted on platforms like AWS or GCP—for storing and transmitting encrypted sync data.

   • Sync updates occur in near real-time.

   • The system uses a differential update model—sending only changes rather than entire datasets—to save bandwidth and speed up syncing.

5. Conflict Handling and Updates
   Arc tracks changes using timestamps and unique data identifiers.

   • If a user makes conflicting changes on multiple devices, Arc typically resolves them using a “last-write-wins” model.

   • The browser’s interface subtly refreshes to show updates without interrupting the user’s workflow.

6. Privacy Controls
   Arc provides granular privacy settings under its account management panel. Users can:

   • Pause synchronization temporarily.

   • View which data categories are being synced.

   • Remove devices or clear synced data manually.

7. Cross-Device Continuity

   • Users can start browsing on their desktop and continue seamlessly on another device.

   • Because Arc syncs the entire workspace structure, even tab groups and pinned sections appear identically across devices.

C. Arc’s Sync Limitations

While powerful, Arc’s sync system is still expanding.

• As of now, Arc is primarily optimized for macOS, Windows, and iOS, but full Android support is still evolving.

• Users must be logged into their Arc account; there’s no manual export/import of sync data yet.

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3. How Sync Works in Vivaldi Browser

A. Vivaldi’s Privacy-First Architecture

Vivaldi’s synchronization is designed around user sovereignty. Unlike most mainstream browsers that depend heavily on big cloud providers, Vivaldi runs its own independent sync servers located in Iceland—an intentional choice due to the country’s strong privacy laws.

Users need a Vivaldi Account to enable sync. Once authenticated, the browser begins syncing selected categories of data.

B. What Vivaldi Syncs

Vivaldi allows users to choose which data categories to sync, including:

• Bookmarks and Speed Dials

• Passwords

• Notes

• Open tabs

• Autofill data

• History

• Extensions and themes

• Settings and preferences

C. End-to-End Encryption in Vivaldi

Vivaldi implements true end-to-end encryption (E2EE) for nearly all synchronized data.

• A unique encryption key (often derived from a passphrase provided by the user) is created on the local device.

• This key encrypts the data before sending it to Vivaldi’s sync servers.

• The server never receives or stores the decryption key.

• When another device connects to the sync account, the user must enter the same passphrase to decrypt the synced data locally.

This means even Vivaldi Technologies cannot read your sync content—making it one of the most secure synchronization systems in the browser industry.

D. Technical Backbone

Vivaldi’s sync infrastructure is built on custom servers hosted by the company.

• Transport Security: HTTPS/TLS encryption secures data transmission.

• Incremental Syncing: Like Arc, Vivaldi only uploads and downloads modified data, making sync faster and lighter.

• Device Registration: Each device has a unique ID; users can view all connected devices in the settings panel and revoke any at will.

• Conflict Management: If both devices edit the same data, Vivaldi uses timestamp-based reconciliation or prompts users to choose between versions.

E. Sync Customization and Control

One of Vivaldi’s standout sync features is user control.

• Users can toggle individual sync items on or off.

• They can manually trigger sync rather than waiting for automatic updates.

• Vivaldi allows users to reset sync data remotely from their online account dashboard.

F. Data Transparency

Vivaldi’s commitment to privacy is further reinforced by their transparency:

• They publish detailed documentation on how sync works, including what data is encrypted and how servers handle requests.

• Their servers are located in the European Economic Area (EEA), compliant with GDPR standards.

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4. Comparison Between Arc and Vivaldi Sync Systems

Feature	Arc Browser	Vivaldi Browser
Account Type	Arc Account	Vivaldi Account
Encryption	End-to-end encryption (cloud-managed keys)	End-to-end encryption (user-defined passphrase)
Server Ownership	Third-party cloud (AWS/GCP)	In-house servers in Iceland
Customizability	Minimal (syncs automatically)	High (user controls what to sync)
Transparency	Limited technical disclosure	Full public documentation
Cross-Platform	macOS, Windows, iOS	Windows, macOS, Linux, Android
User Control	Simplified UX for automation	Advanced manual controls
Security Model	Privacy-first, seamless sync	Privacy-first, user-empowered encryption

In summary, Arc focuses on simplicity and seamless user experience, while Vivaldi prioritizes control, transparency, and independence.

Arc’s sync feels almost “magical” to the user—everything just works. Vivaldi’s sync, meanwhile, appeals to advanced users who want to know exactly how and where their data is stored and encrypted.

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5. Security and Privacy Considerations

Both browsers implement strong privacy safeguards that go beyond what’s offered by Chrome or Edge:

1. End-to-End Encryption:
   Ensures only the user can decrypt synced data.

2. Two-Factor Authentication (2FA):
   Available for Arc and Vivaldi accounts to prevent unauthorized access.

3. Local Decryption:
   Data remains unreadable outside the user’s authorized devices.

4. Manual Device Management:
   Users can view all synced devices and revoke access remotely.

5. Transparency:
   Vivaldi openly discloses its sync process and security architecture, while Arc focuses on intuitive privacy without burdening users with technical details.

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6. Challenges and Limitations

Even the best-designed sync systems face certain constraints:

• Device Delays: Sync might not be instantaneous depending on internet speed and device state.

• Version Conflicts: Editing the same bookmark on two devices can lead to duplication or overwriting.

• Offline Handling: Changes made offline must queue until the device reconnects.

• Platform Gaps: Arc is still expanding to Android, while Vivaldi’s iOS version launched recently and is still maturing.

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7. Future of Sync in Browser-Based Apps

Both Arc and Vivaldi are pushing the boundaries of what browser sync can achieve:

• Real-Time Collaboration: Future versions may enable live tab sharing or team-based workspace sync.

• AI-Powered Sync Optimization: Predictive syncing could prioritize frequently used data.

• Zero-Knowledge Encryption: Broader implementation ensuring zero visibility for companies over user data.

• Federated Sync Models: Allowing users to host their own sync servers for ultimate control.

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8. Conclusion

Synchronization in browsers like Arc and Vivaldi demonstrates the evolution of web technology—from simple bookmark sharing to encrypted, intelligent, and user-centric ecosystems.

Arc emphasizes effortless, cloud-powered continuity, making syncing invisible to the user. Everything “just works,” integrating perfectly into its productivity-driven design.

Vivaldi, on the other hand, prioritizes privacy, independence, and transparency, allowing users to manage exactly what is synced, when, and how.

Both approaches reveal that the future of browser sync isn’t just about convenience—it’s about giving users freedom, control, and trust in how their digital worlds stay connected.