Bcrypt

Hash and verify passwords with bcrypt

Password Security

🔒 100% client-side — your data never leaves this page

Maintained by ToolsKit Editorial Team•Updated: March 23, 2026•Reviewed: April 1, 2026

Editorial Policy/Privacy/Report issue

English version/Chinese version

Page mode

Input

Quick CTA

Enter a password first to generate a bcrypt hash or verify a match immediately; cost tuning and scenarios stay in Deep.

Plain text password

Cost factor (rounds: 2^10 = 1,024)

Recommended — good balance

🔒 100% client-side · Web Crypto API

Output

Hash will appear here

Next step workflow

Generate stronger passwords Compare hash algorithms Generate secure tokens

Page reading mode

Deep expands pitfalls, recipes, snippets, FAQ, and related tools when you need troubleshooting or deeper follow-through.

About this tool

Generate bcrypt password hashes with a configurable cost factor (4-14), or verify a plaintext password against an existing bcrypt hash. The hash breakdown explains the algorithm prefix, cost factor, salt, and hash sections. Uses PBKDF2 via the Web Crypto API for secure computation in your browser.

Failure Input Library

Hash column length too short in database

Bad input: DB column truncates bcrypt hash string during write.

Failure: Users cannot log in even with correct password.

Fix: Expand column length and validate full hash persistence in integration tests.

Cost factor raised without capacity validation

Bad input: Increase bcrypt rounds globally during traffic growth week.

Failure: Authentication latency spikes and timeout alarms trigger.

Fix: Load-test first and roll out cost changes gradually with monitoring.

Hash prefix mismatch across libraries

Bad input: Service A emits `$2y$` while service B only accepts `$2b$` handling.

Failure: Valid credentials fail after service migration.

Fix: Standardize bcrypt library behavior and test cross-service compatibility vectors.

Truncated password handling ignored

Bad input: Very long passphrases are silently truncated by old integration layers.

Failure: Users cannot reproduce expected login behavior across clients.

Fix: Document max-length policy and enforce pre-hash validation consistently.

Quick Decision Matrix

Production auth system with long lifecycle

Recommend: Use benchmarked adaptive cost and rehash-on-login strategy.

Avoid: Avoid static legacy cost settings without periodic review.

Need stronger password storage policy over time

Recommend: Tune cost using real latency budgets and progressive rehash strategy.

Avoid: Avoid static one-time settings that ignore hardware and traffic changes.

Consumer-facing production authentication

Recommend: Use adaptive cost policy, server-side verify, and rehash-on-login.

Avoid: Avoid fixed legacy cost factors kept unchanged for years.

Short-lived sandbox demos

Recommend: Use simplified cost for speed with clear non-production labeling.

Avoid: Avoid promoting demo settings into production configuration.

Production Snippets

Bcrypt prefix sample

txt

$2b$10$...

Compare & Decision

Hashing vs encryption

Hashing

Use it for password storage and one-way verification.

Encryption

Use it for data that must later be decrypted.

Note: Passwords usually need hashing, not reversible encryption.

Lower cost for latency vs higher cost for security margin

Cost 10 baseline

Use for non-critical internal systems with strict latency caps.

Cost 12+ migration

Use for user-facing production authentication.

Note: Cost policy should be benchmarked and periodically reviewed, not fixed forever.

Immediate global cost bump vs phased migration

Phased migration

Use for large user bases with strict SLOs.

Immediate global bump

Use for tiny systems where latency impact is negligible.

Note: Hash-cost upgrades are safer when tied to observed latency budgets.

Static bcrypt cost vs adaptive cost migration

Static cost

Use for short-lived internal test systems.

Adaptive migration

Use for long-term production auth with evolving hardware.

Note: Adaptive migration keeps security posture current without forced password resets.

Client-side hash only vs server-side verify contract

Client-side only

Use only as a transport-hardening layer.

Server-side verify

Use as the real authentication control boundary.

Note: Server-side verification remains mandatory for trustworthy auth decisions.

Direct Answers

Q01

Is bcrypt for encryption or password hashing?

It is for password hashing, which is intentionally one-way rather than reversible.

Q02

Does a higher cost always mean better?

Higher cost improves resistance, but it also raises runtime cost and should match the real environment budget.

Failure Clinic (Common Pitfalls)

Treating demo hashing as production policy

Cause: Hashing samples is not the same as designing a full password storage or auth strategy.

Fix: Use the tool for inspection and examples, then rely on vetted libraries and policies in production.

Scenario Recipes

Hash a password sample for testing

Goal: Generate or verify a bcrypt-style password hash during auth workflow checks.

Choose hash or verify mode.
Enter the password and cost or the existing hash to verify against.
Use the result for testing and comparison, not as a full production password-policy replacement.

Result: You can sanity-check password-hash flows without wiring a full auth system.

Rehash-on-login cost upgrade

Goal: Increase bcrypt strength without forcing global password resets.

Keep existing hashes valid for verification.
After successful login, rehash with target higher cost.
Track migration coverage until old-cost population is near zero.

Result: Security posture improves gradually with minimal user friction.

Cost factor rollout without auth outage

Goal: Increase password hash strength gradually while keeping login latency stable.

Measure current login p95 with existing cost setting.
Raise cost one step in canary and monitor auth latency/error budget.
Rehash on successful login to migrate users progressively.

Result: Security posture improves without causing auth performance incidents.

Password hash cost tuning for login peak hours

Goal: Keep brute-force resistance high without hurting authentication latency.

Benchmark candidate cost factors under realistic concurrent login load.
Set SLO guardrails for p95 login time before selecting final cost.
Schedule gradual rehash-on-login migration for older hashes.

Result: Hash strength and login performance stay balanced at scale.

Cost-factor rollout without login disruption

Goal: Upgrade bcrypt strength while keeping existing users active.

Set a target cost policy and detection threshold.
Verify incoming password against stored hash on login.
Rehash with new cost after successful authentication.

Result: Hash strength upgrades gradually with minimal user friction.

Practical Notes

Bcrypt works best when you apply it with clear input assumptions and a repeatable workflow.

Security boundary

Treat cryptographic output as part of a broader security workflow, not a standalone guarantee.

Clarify algorithm choice, key handling, and rotation policy before integrating into production.

Operational safety

Never expose secrets in logs or screenshots when testing cryptographic flows.

Use fixed test vectors in CI to detect accidental behavior changes early.

Use It In Practice

Bcrypt is most reliable with real inputs and scenario-driven decisions, especially around "Production auth system with long lifecycle".

Use Cases

When Production auth system with long lifecycle, prioritize Use benchmarked adaptive cost and rehash-on-login strategy..
When Need stronger password storage policy over time, prioritize Tune cost using real latency budgets and progressive rehash strategy..
Compare Hashing vs Encryption for Hashing vs encryption before implementation.

Quick Steps

Choose hash or verify mode.
Enter the password and cost or the existing hash to verify against.
Use the result for testing and comparison, not as a full production password-policy replacement.

Avoid Common Mistakes

Common failure: Users cannot log in even with correct password.
Common failure: Authentication latency spikes and timeout alarms trigger.

Frequently Asked Questions

What is bcrypt?

Bcrypt is a password hashing function designed to be slow and expensive to compute. This makes brute-force and rainbow table attacks impractical. It is the recommended algorithm for storing user passwords.

What cost factor should I use?

A cost factor of 10-12 is recommended for most applications. Higher values are more secure but take longer to compute. Cost 10 typically takes 100-300ms, which is slow enough for attackers but fast enough for users.

Can I use this hash in my application?

The hash format is compatible with standard bcrypt implementations in Node.js (bcryptjs), Python (bcrypt), PHP (password_hash), and most other languages.

Is the computation done in my browser?

Yes. All hashing uses the Web Crypto API (PBKDF2) and runs entirely client-side. Your passwords are never transmitted.

Is this cryptographic output secure enough for production?

Bcrypt is useful for quick client-side generation and inspection, but production security depends on algorithm choice, key management, and backend verification policies.

Are keys or secrets uploaded anywhere?

No. Inputs stay in your browser and are not transmitted to servers by this tool.