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HashMyWords guide

Timestamp a file without uploading it

Create a verifiable timestamp for a document, image, video, archive or other digital file while the original file stays on your device.

Create a file proofLearn how it works

Free · no account required

What does a file timestamp show?

A file timestamp creates evidence that the standard SHA-256 of an exact set of file bytes was recorded by a particular time. If the file changes later, its SHA-256 changes and it will no longer match the recorded value.

Important: a matching file proof can help demonstrate that the exact file bytes you hold correspond to the earlier timestamped SHA-256. It does not, by itself, prove authorship, legal ownership, when the file was originally created, or whether its contents are true.

How HashMyWords creates a file proof

Choose the fileSelect the document, image, video, archive or other digital file you want to preserve.
Hash it locallyYour browser calculates the file's SHA-256 on your device. The file itself is not uploaded to HashMyWords.
Record the SHA-256HashMyWords records that exact 64-character SHA-256 on Hedera HCS. No second file hash is derived for new H2 proofs.
Save your proof materialKeep the original file, receipt or certificate, secret code and verification link so the record can be checked later.

File stays local; SHA-256 is public

The original file and filename are not uploaded to HashMyWords. Your browser calculates the standard SHA-256 locally, then HashMyWords submits that exact digest as public proof data on Hedera HCS.

A SHA-256 can itself be sensitive when underlying material is predictable or already known. Create an H2 file proof only when you are comfortable with the file hash being public and persistent.

What should you keep?

Keep the exact original file. Also keep the HashMyWords receipt or certificate and the secret code. The receipt records useful local metadata and the verification link; the shareable certificate deliberately excludes the secret code.

If the file matters as evidence, preserve surrounding context too: source records, drafts, correspondence, version history or other material that helps explain where it came from and who controlled it.

How do you verify the file later?

Open the verification link saved with the proof. HashMyWords checks the HCS message and recorded SHA-256 against Hedera's public Mirror Node. You can then choose a local file and HashMyWords hashes it again in your browser.

If the locally calculated SHA-256 exactly matches the one recorded in the referenced H2 HCS message, the selected file is an exact byte-for-byte match for the file represented by that proof. Historical H1 proofs remain verifiable using their original format.

Frequently asked questions

Does HashMyWords upload my file?

No. The file itself stays in your browser. For new H2 proofs, HashMyWords receives and publicly records the standard SHA-256 plus the proof data needed for timestamping.

What file types can I timestamp?

The File Proof tool is designed for general digital files such as documents, images, video, archives and other file types.

What happens if I edit the file later?

Even a small byte-level change normally produces a different SHA-256, so the changed file will not match the earlier recorded digest.

Do I need the secret code to prove an exact file match?

The public file-proof verification link checks the Hedera evidence and lets you compare a local file. The secret code is separate proof material that confirms control of the HashMyWords record and should still be kept private.

Continue in the Guide

Protect a PDF before AIHarden and timestamp a PDF before uploading it to ChatGPT, Claude, Gemini, Microsoft Copilot or another AI tool.Timestamp text onlineTimestamp text online for free. Create a verifiable Hedera record of your words and keep a secret code so you can verify the same text later.Verify a proofLearn how to verify a HashMyWords proof using a secret code or, for file proofs, compare an exact local file with the proof hash recorded on Hedera.Proof of existenceLearn how digital proof of existence works and create a verifiable timestamp that can help show matching content existed by a certain time.Hedera timestampingLearn how cryptographic timestamping works, what a proof hash can demonstrate, and how HashMyWords records proof hashes through Hedera Consensus Service.
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