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SHA1 Hash Generator

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Don't use SHA-1 for security purposes. A practical collision attack (SHAttered, 2017) means it's no longer safe for signatures or certificates — fine for Git hashes and non-adversarial checksums only.

Generate a SHA-1 hash from text or a file live, entirely in your browser — with no arbitrary file size cap, and a clear warning that SHA-1 shouldn't be used for security purposes.

How it works

  1. Type text, or switch to the File tab and choose a file (no size limit)
  2. The SHA-1 hash updates live below — no button, files hashed locally, never uploaded
  3. Copy the hash or download it as a .txt file

Frequently asked questions

Is SHA-1 safe for digital signatures or certificates?

No. A practical collision attack (SHAttered, 2017) means all major browsers and certificate authorities now reject SHA-1. It's fine for Git commit hashes and non-adversarial checksums, but not for security-critical use.

Is there a file size limit?

No artificial cap — it's limited only by what your browser can handle.

Does this update live?

Yes, no button to click.

#Sha1HashGenerator#Sha1HashGeneratorFileNoSizeLimit#Sha1CollisionWarningTool#Sha1OnlineLiveNoButton

Related tools

MD5 Hash Generator MD5 Hash Generator SHA-256 Hash Generator SHA-256 Hash Generator

From the blog

One SHA-1 generator we checked never mentions that SHA-1 is cryptographically broken. Another caps files at 50MB for no real reason.
dev

One SHA-1 generator we checked never mentions that SHA-1 is cryptographically broken. Another caps files at 50MB for no real reason.

SHA-1 has had a practical collision attack since 2017, but sha1-online.com's page doesn't mention it anywhere. A tool that does warn about it still needs a button click and stops at 50MB files. Ours warns clearly, updates live, and doesn't cap file size.

2026-08-29

Update history

  • 2026-08-30 Added: a cover image — used as the card thumbnail, social share image, and blog title image.
  • 2026-08-29 Launched: live SHA-1 hashing (text and file, no button, no arbitrary file size cap), explicit warning about SHA-1's known collision vulnerability (SHAttered).