SHA1 File Checksum
Calculate SHA-1 or HMAC-SHA-1 for a local file or URL in your browser, primarily for legacy checksum compatibility. Read more
Calculate a SHA-1 file checksum
This tool reads a local file or accessible URL and calculates its 160-bit SHA-1 digest. Local files are processed in the browser rather than uploaded to an application server. Hex and Base64 output plus optional HMAC are supported.
Use SHA-1 when reproducing an existing legacy checksum. For new integrity workflows, prefer SHA-256 or a stronger current algorithm because SHA-1 no longer provides adequate collision resistance against an attacker.
How to hash a file with SHA-1
- Choose Local File or URL.
- Select the source and desired output encoding.
- Enable HMAC only when a shared secret and protocol require it.
- Calculate and compare the entire digest with a trusted value.
URL access depends on the remote server’s cross-origin policy. A file that opens in a browser may still block programmatic reading.
What a checksum proves
Matching SHA-1 values are useful for accidental-change checks and legacy compatibility, but a checksum copied from the same compromised location as the file is not independent evidence. Prefer a trusted authenticated source and a stronger digest.
NIST FIPS 180-4 defines SHA-1. HMAC-SHA-1 is a different keyed construction and must not be confused with an ordinary file digest.
SHA-1 file FAQ
Does the filename affect the checksum?
No. Only the file bytes are hashed.
Why does my checksum differ?
The file may be incomplete, modified, transformed in transit, or compared using another output representation.
What should I use for a new checksum?
Use SHA-256 File Checksum unless the relevant specification requires another algorithm.
