パスワードマネージャー徹底比較 - 選び方の決定版ガイド

About 16 min read

Choosing a password manager is one of the most impactful security decisions you can make, yet the market offers dozens of options with overlapping features and confusing pricing. Should you trust a cloud-based service or keep everything local? Is the free tier sufficient, or do paid plans offer meaningful security advantages? This guide cuts through the marketing noise with a systematic comparison framework based on security architecture, usability, cross-platform support, family sharing capabilities, and data migration paths. Rather than declaring a single winner, we help you identify which type of password manager aligns with your specific threat model and workflow requirements.

Cloud vs Local - Fundamental Architecture Differences

Cloud-Based Architecture and Security Model

Cloud-based password managers (1Password, Bitwarden, Dashlane, LastPass, etc.) store encrypted data on the provider's servers and automatically sync across multiple devices. Crucially, all trustworthy cloud services employ zero-knowledge architecture. This means the service provider itself cannot access users' master passwords or decryption keys. Data is encrypted on the user's device before being sent to servers, and only encrypted data exists on the server.

The greatest advantage of cloud-based managers is convenience. Adding a new device requires only entering your master password to access all data, and synchronization between devices is automatic. The risk, however, is server-side security breaches. In the 2022 LastPass incident, encrypted vault data was obtained by attackers. Due to zero-knowledge design, users with strong master passwords remained safe, but those with weak master passwords were exposed to offline brute-force attack risks.

Local Architecture and Operational Costs

Local password managers (KeePass, KeePassXC, etc.) store encrypted database files only on the user's device. Since no data is sent to servers, server breach risk is zero. From a security perspective, this is the most robust approach, but using multiple devices requires manual synchronization. Syncing database files via Dropbox or Google Drive is possible but essentially carries similar risks to cloud-based solutions (though the risk is limited since the cloud storage provider lacks the database decryption key).

Feature Comparison and Family Plans of Major Services

Security Feature Comparison

The three most important security features when choosing a password manager are encryption method, two-factor authentication support, and security audit track record. For encryption, the current industry standard is AES-256-bit encryption with PBKDF2 (or Argon2) key derivation. 1Password adds a proprietary Secret Key making decryption impossible with the master password alone, increasing resistance to server breaches. Bitwarden uses Argon2id for key derivation, strengthening resistance to GPU-based brute-force attacks. For 2FA, all major services support TOTP, but hardware security key (FIDO2/WebAuthn) support is available in 1Password, Bitwarden, and Dashlane.

Family plans are extremely useful for managing the entire family's security collectively. 1Password Families ($4.99/month, up to 5 people) has robust shared vault features for safely sharing Wi-Fi passwords and streaming service accounts. Bitwarden Families ($3.33/month, up to 6 people) offers open-source transparency at a low price. Dashlane Family ($7.49/month, up to 10 people) includes VPN functionality and dark web monitoring. When choosing a family plan, ease of use matching family members' IT literacy is also an important criterion.

Data Migration and Security Architecture Differences When Switching

Steps for Smooth Data Migration

Switching password managers is not as difficult as many imagine. Nearly all password managers support CSV export/import. The basic migration steps are: (1) export data as CSV from current service, (2) import CSV into new service, (3) verify data migrated correctly after import, (4) securely delete the CSV file after confirmation (use a file shredder), (5) delete the old service account. Note that CSV export files contain all passwords in plain text, so handle the file with extreme care during the migration process.

For migrations between 1Password and Bitwarden (in either direction), dedicated importers are available that allow direct migration without going through CSV. This avoids the risk of plain-text passwords existing on the filesystem even temporarily. After migration, don't forget to completely delete data remaining in the old service. Also consider regenerating all passwords during the migration. Some old passwords may not meet current strength standards. Generate new strong passwords with Passtsuku.com to elevate your security level simultaneously with the migration. Combining with <AmazonLink keyword="YubiKey" locale={locale} className="amazon-inline-link">hardware keys like YubiKey (Amazon)</AmazonLink> further strengthens your password manager security.

Summary of Selection Criteria

The final choice depends on your priorities. If convenience and automatic sync are top priority, choose a cloud-based option (1Password or Bitwarden). To minimize costs, Bitwarden's free plan is optimal. If you value open-source transparency and self-hosting options, Bitwarden is the clear choice. For maximum security and complete data self-management, choose KeePassXC. For family use, 1Password Families offers the least friction for members who aren't tech-savvy. Regardless of which service you choose, using any password manager is overwhelmingly safer than using none. Starting today with something is more important than delaying while pursuing the perfect choice.