Use case

Timestamp a document

Timestamping a document means proving it existed at a specific date through a trusted third party. Proxae computes the SHA-256 hash of your file in your browser and anchors it in the Bitcoin blockchain — without ever accessing the content.

Need to prove a document existed at a specific date? Proxae generates a cryptographic fingerprint of your file and anchors it in the Bitcoin blockchain — without ever accessing its content.

Timestamp a document →

Why timestamp?

A file on your computer can be modified at any time. Its modification date proves nothing. To establish a certain date, you need a trusted third party. The Bitcoin blockchain plays that role — immutably and verifiable by anyone.

Real-world examples

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A law firm timestamps case files to establish their date of existence in case of dispute.

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A photographer certifies photos before publishing online — proof of authorship in case of unauthorized reuse.

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A company timestamps quarterly financial reports to prove they existed before an audit date.

How it works

Upload your file

The SHA-256 fingerprint is computed in your browser. The file never leaves your device.

Anchoring in Bitcoin

The fingerprint is submitted to OpenTimestamps servers and anchored in a Bitcoin block in ~3 hours.

Verifiable certificate

You receive a permanent link and an OTS receipt. With the Pro plan, a PDF certificate and an RFC 3161 timestamp are also available.

Need to prove a document's date? Timestamping is instant, free, and confidential.

Timestamp a document

Proxae vs other timestamping methods

	Proxae	Notary	Centralized service
Cost	✓ Free	$200+	Varies
Speed	✓ Instant	By appointment	Fast
Privacy	✓ Full (local hash)	Document handed over	File uploaded
Permanence	✓ Permanent (Bitcoin)	Legal duration	Depends on service

Advantages

✦ All file formats accepted (PDF, images, videos, archives...)
✦ No size limit — only the hash is processed
✦ Total privacy — the file stays on your device
✦ Permanent proof, independent of any centralized service

Frequently asked questions

What file formats are accepted?

All of them. Proxae computes a SHA-256 hash of the file, regardless of format. PDF, images, videos, source code, ZIP archives — everything works.

Is the file stored on your servers?

No. The hash is computed in your browser. Only the 64-character fingerprint is sent — never the file itself.

How do I verify a timestamp later?

Go to proxae.com/verify or use any OpenTimestamps client. Recompute the hash of your file and compare it with the recorded proof.

Does timestamping have legal value?

Yes. Blockchain timestamping constitutes evidence. The RFC 3161 certificate (Pro plan), compliant with eIDAS, is recognized by European courts as a qualified timestamp.

What is the difference with a notarized timestamp?

A notary provides an authentic deed but costs $200+, requires an appointment, and you must hand over the document. Proxae is instant, free, and your file never leaves your device.

Timestamp a document

Free, private, in 10 seconds.