Tom's Quick Hash Checker – Instructions (Free)

1) What is this?

Tom's Quick Hash Checker is a small Windows utility that calculates file hashes and helps you verify that a file you downloaded is exactly the file the publisher intended.

Hash = fingerprint: if even one byte of a file changes, the hash changes completely. That makes hashes great for integrity checks and tamper detection.

2) Two main use cases

Publish checksums (for your downloads)

Create a SHA-256 hash for your ZIP/EXE and paste it onto your website so users can verify their download.

Compute SHA-256 (default)
Copy hash to clipboard
Save .sha256 file beside the download

Verify a downloaded file (security check)

Paste the expected hash (from the website) and verify with a clear MATCH / MISMATCH result.

Drag & drop the downloaded file
Paste expected hash
App auto-normalizes formatting

3) Quick start

Launch TomsQuickHash.exe.
Drag & drop a file into the window.
Wait for the status to show Done.
Select the file in the list to enable copy/save actions.

Tip: SHA-256 is the recommended default for modern checksum publishing.

4) Compute a hash (and copy it)

After hashing is complete, you can copy either:

Copy Hash — copies only the hash value (cleanest for websites).
Copy Line — copies hash filename (handy for logs/notes).

Website best practice: publish the SHA-256 hash value on your download page, and optionally offer a .sha256 file for advanced users.

5) What is the .sha256 file?

Clicking Save .sha256 creates a small text file next to your download:

YourFile.zip.sha256

The file contains this standard format:

a1b2c3d4e5f6...  YourFile.zip

This format is compatible with common checksum tools (including sha256sum on Linux/Mac).

6) Verify a downloaded file (MATCH / MISMATCH)

Download the file you want to verify (ZIP/EXE).
Drag & drop it into Tom’s Quick Hash Checker.
Copy the expected SHA-256 hash from the website.
Paste it into the Verify Hash box.
Click Verify and check the result.

Smart verification: ignores spaces, line breaks, case, and prefixes like SHA256:.

7) Supported algorithms

Algorithm	Output Length	Notes
SHA-256	64 chars	Recommended default (modern + widely used)
SHA-512	128 chars	Extra-long hash (optional)
SHA-1	40 chars	Legacy (not recommended for security)
MD5	32 chars	Legacy (use only for quick non-security checks)

8) System requirements

Windows 10 or Windows 11
No install required
No extra runtime required

9) Troubleshooting

"Access denied" when hashing a file

The file is locked by another program or needs admin access.
Close anything using the file and try again.
If needed, run the tool as Administrator.

Windows SmartScreen warning

Right-click the EXE → Properties → check Unblock → OK.
This is common for new portable utilities.

Hash doesn't match

Re-download the file (incomplete downloads can happen).
Make sure you’re comparing the same algorithm (SHA-256 vs SHA-512).
Copy/paste the hash again (your tool ignores spaces/case, but websites sometimes wrap lines).

10) Technical details (for nerds)

Language: C++17
UI: Win32 native
Hashing: Windows CNG/BCrypt (built into Windows)
Threading: background worker thread so large files don’t freeze the UI
Dependencies: none