SHA-1 Hash Generator Online — Free SHA-1 Checksum Tool
Use this free online SHA-1 hash generator to compute a SHA-1 checksum for any text string, local file, or remote URL — no software to install and no account needed. HMAC mode lets you apply a secret key for message-authentication use cases.
What is SHA-1?
SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function developed by the U.S. National Security Agency and published by NIST in 1995. It processes input data of any size and produces a fixed 160-bit (40 hexadecimal character) digest. Like all hash functions, even the smallest change to the input produces a completely different output — a property known as the avalanche effect.
SHA-1 is a member of the SHA family, which also includes the stronger SHA-224, SHA-256, SHA-384, and SHA-512 variants. It has been deprecated for security-critical uses since 2017 after practical collision attacks were demonstrated, meaning two different inputs can produce the same hash. It is not suitable for password storage or digital signatures.
What is SHA-1 used for?
Despite its security limitations, SHA-1 remains widely encountered for non-security-critical tasks where a fast, compact fingerprint is sufficient:
- File integrity checks — verify that a downloaded file has not been corrupted or tampered with by comparing checksums.
- Version control — Git historically used SHA-1 to uniquely identify commits and objects in a repository.
- Legacy system compatibility — older protocols and software may still produce or expect SHA-1 checksums.
- Data deduplication — quickly detect duplicate files or data blocks in storage systems.
- HMAC-SHA1 — keyed hashing for API authentication tokens (e.g. OAuth 1.0) where the secret key is kept private.
SHA-1 vs. other hash algorithms
When choosing a hash algorithm, the right choice depends on your requirements. For general-purpose file verification where speed matters, SHA-1 or MD5 both work well. For any security-sensitive application — digital certificates, code signing, or password hashing — prefer SHA-256 or SHA-512. This tool supports all major algorithms side by side, so you can generate and compare multiple digests for the same input in one place.
Frequently asked questions
Is this SHA-1 tool free to use?
Yes, the tool is completely free. There is no account, subscription, or software download required — just paste your text or upload a file and click to generate the hash.
Can I hash a file instead of typed text?
Yes. You can upload a file from your device or supply a remote URL. The tool will compute the SHA-1 checksum over the full file content.
What happens to files I upload?
Uploaded files are processed on the server to compute the hash and are then deleted automatically. They are not stored, shared, or used for any other purpose.
Is SHA-1 safe to use for passwords or digital signatures?
No. SHA-1 has known collision vulnerabilities and has been deprecated for security-critical uses since 2017. For passwords use a dedicated password-hashing function; for signatures use SHA-256 or SHA-512.
What is HMAC-SHA1 and when should I use it?
HMAC-SHA1 combines SHA-1 with a secret key to produce a message authentication code (MAC). It is used in protocols like OAuth 1.0 to verify that a message comes from a trusted sender and has not been altered in transit.