bcrypt vs Argon2

Differences, use cases, and when to use each

Last updated: April 6, 2026

Both are password hashing algorithms designed to be slow. bcrypt is the established standard (1999). Argon2 is the newer standard (2015 PHC winner) with memory-hardness that resists GPU and ASIC attacks better.

Quick Comparison

Feature	bcrypt	Argon2
Age	1999 (established)	2015 (modern)
Memory Hardness	No (CPU-only)	Yes (configurable memory)
GPU Resistance	Moderate	Strong (memory-bound)
Configuration	Work factor (rounds)	Time, memory, parallelism
Max Password Length	72 bytes	No practical limit

When to Use Each

When to Use bcrypt

Use bcrypt when it's already in your stack, when using older systems, or when Argon2 isn't available. bcrypt remains secure and is widely supported.

When to Use Argon2

Use Argon2 for new projects. Its memory-hardness provides better protection against GPU-based cracking, and it has no password length limitation.

Pros & Cons

bcrypt

Battle-tested for 25+ years

Available in every language

Well-understood security

72-byte password limit

Not memory-hard

Argon2

Memory-hard (GPU resistant)

Configurable memory/time/parallelism

No password length limit

PHC winner

Newer, less battle-tested

Not available in all environments

Verdict

Argon2 for new projects; bcrypt is fine for existing systems. Both are vastly better than MD5, SHA-256, or any fast hash for passwords.

Key Takeaways: bcrypt vs Argon2

Choosing between bcrypt and Argon2 depends on your specific requirements, not on which format is “better” in absolute terms. Both exist because they solve different problems well. In professional projects, you will often use both — the key is understanding which context calls for which tool.

If you are starting a new project and have flexibility in choosing your data format or tool, consider your team's familiarity, your ecosystem requirements, and the long-term maintenance implications. The comparison table and pros/cons above should help you make an informed decision for your specific situation.

Switching Between bcrypt and Argon2

If you need to convert or migrate between bcrypt and Argon2, our tools can help. Use the interactive tools linked below to convert data formats instantly in your browser, or explore the code examples in our language-specific guides for programmatic conversion in your preferred language.

When migrating a project from one to the other, start with a small subset of your data, validate the output thoroughly, and then automate the full conversion. Always keep a backup of your original data until you have verified the migration is complete and correct.

Try the Tools

Hash Generator

Frequently Asked Questions

Should I migrate from bcrypt to Argon2?

If bcrypt is working well, migration isn't urgent — it's still secure. For new projects, choose Argon2. You can progressively migrate by re-hashing with Argon2 when users log in.

What are the differences between Argon2i, Argon2d, and Argon2id?

Argon2d is faster and resistant to GPU attacks but vulnerable to side-channel attacks. Argon2i is resistant to side-channel attacks. Argon2id combines both — use Argon2id for password hashing as it provides the best balance of security against all known attack vectors.

What memory and time parameters should I use for Argon2?

OWASP recommends Argon2id with minimum 19MB memory, time cost of 2, and parallelism of 1 as a starting point. Increase memory to 64MB or more if your server can handle it. The goal is 100-500ms per hash — tune parameters to hit this target on your hardware.

Is Argon2 available in languages like PHP, Python, and Node.js?

Yes. PHP has password_hash() with PASSWORD_ARGON2ID since PHP 7.3. Python has argon2-cffi. Node.js has argon2 (npm package). Java has Bouncy Castle. All major languages have production-ready Argon2 implementations, though availability varies by hosting environment.

Why does Argon2's memory-hardness matter against GPU and ASIC attacks?

GPUs and ASICs have massive parallel compute but limited memory per core. bcrypt is CPU-hard but runs fine on GPUs. Argon2 requires large memory allocations per hash, which limits GPU parallelism because each concurrent hash needs its own memory block — making custom cracking hardware impractical.

How do I handle password hash upgrades during a bcrypt-to-Argon2 migration?

Re-hash on login: when a user authenticates, verify with bcrypt, then re-hash the plaintext password with Argon2 and update the stored hash. Store a version identifier with each hash so your code knows which algorithm to use for verification. This avoids forcing password resets.

Related Comparisons

SHA-256 vs bcrypt MD5 vs SHA-256

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Reviewed by

Tamanna Tasnim

Senior Full Stack Developer

ToolsContainerDhaka, Bangladesh5+ years experiencetasnim@toolscontainer.com www.toolscontainer.com

Full-stack developer with deep expertise in data formats, APIs, and developer tooling. Writes in-depth technical comparisons and conversion guides backed by hands-on engineering experience across modern web stacks.

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