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SHA-1 vs SHA-256

Differences, use cases, and when to use each

Last updated: April 6, 2026

SHA-1 (160-bit) has been deprecated for security use after practical collision attacks were demonstrated in 2017. SHA-256 (256-bit) remains secure and is the recommended replacement.

Quick Comparison

FeatureSHA-1SHA-256
Hash Size160-bit (40 hex chars)256-bit (64 hex chars)
SecurityDeprecated (collisions demonstrated)Secure
Git UsageUsed by Git (being migrated)Git's migration target
Certificate UsageRejected by browsers since 2017Current standard

When to Use Each

When to Use SHA-1

Avoid SHA-1 for new applications. It's only acceptable in legacy systems being migrated, and in Git (which is transitioning to SHA-256).

When to Use SHA-256

Use SHA-256 as the default hash function for all new applications. It's secure, widely supported, and the recommended standard by NIST.

Pros & Cons

SHA-1

Faster than SHA-256
Shorter output
Deprecated for security
Collision attacks demonstrated

SHA-256

Cryptographically secure
NIST recommended
Long-term security
Slightly slower
Longer hash strings

Verdict

Always use SHA-256 over SHA-1. SHA-1 is deprecated by NIST, rejected by browsers, and has demonstrated collisions. The performance difference is negligible.

Key Takeaways: SHA-1 vs SHA-256

Choosing between SHA-1 and SHA-256 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 SHA-1 and SHA-256

If you need to convert or migrate between SHA-1 and SHA-256, 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

Is SHA-1 still used anywhere?
Git uses SHA-1 for commit hashing (collision resistance isn't critical for its use case, and migration to SHA-256 is underway). Some legacy systems still use it but should migrate.
How was SHA-1 actually broken, and what does that mean in practice?
Google's SHAttered attack (2017) demonstrated the first practical SHA-1 collision — two different PDF files with the same SHA-1 hash. The attack required ~6,500 GPU-years of computation. While expensive, it proved SHA-1 collisions are feasible for well-funded attackers.
Will Git's migration from SHA-1 to SHA-256 break existing repositories?
Git's SHA-256 migration is backward-compatible. Repositories can be converted, and Git supports interoperability between SHA-1 and SHA-256 repos. Existing SHA-1 commit hashes will be mapped to new SHA-256 hashes during conversion. The transition is designed to be seamless.
Is HMAC-SHA-1 also insecure, or just plain SHA-1?
HMAC-SHA-1 is still considered secure because HMAC's construction prevents collision attacks from compromising message authentication. However, migrating to HMAC-SHA-256 is recommended for new implementations to avoid future risk and satisfy compliance requirements.
When did browsers stop accepting SHA-1 certificates?
Chrome, Firefox, and Edge stopped accepting SHA-1 SSL/TLS certificates in early 2017. Certificate authorities had already stopped issuing them by January 2016. Any SHA-1 certificate encountered today is rejected with a hard error, not just a warning.
Does SHA-256 have any known weaknesses or theoretical attacks?
No practical attacks exist against SHA-256. Length extension attacks affect plain SHA-256 (use HMAC to prevent this), but no collision or preimage attacks are known. SHA-256 is expected to remain secure for decades with current computational capabilities.

Related Comparisons

MD5 vs SHA-256SHA-256 vs SHA-512

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Reviewed by

Tamanna Tasnim

Senior Full Stack Developer

ToolsContainerDhaka, Bangladesh5+ years experiencetasnim@toolscontainer.comwww.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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