ProofStamp can preserve the fingerprint of a file in several different ways.
The basic idea stays the same:
Your file → SHA-256 fingerprint → evidence
Your original file stays with you. What changes is where the evidence is recorded, how time is established, and how someone can check it later.
Today you can choose between ProofStamp via Email, nStamp, ProofStamp via Bitcoin, and ProofStamp via Arbitrum.
There is no single “best” option. Each is useful for a different job.
Start with the simple version
For most everyday situations, ProofStamp via Email is the easiest place to start.
Want a public blockchain timestamp? Look at nStamp.
Want a portable OpenTimestamps proof anchored to Bitcoin? Use ProofStamp via Bitcoin.
Want to explore a passkey-based blockchain workflow? Try the Arbitrum testnet prototype.
Here is what changes between them.
ProofStamp via Email
Best for everyday evidence
ProofStamp via Email creates the SHA-256 fingerprint of your file in your browser.
The file is not uploaded to ProofStamp.
You can email the ProofStamp, save it as a text file, or copy it. If you send it by email, the email provider’s received time gives you a separate record of when that ProofStamp reached the inbox.
There is no ProofStamp account and no wallet.
That makes it useful for photos, PDFs, screenshots, submitted forms, work records, and documents you may need to identify later.
If you want a practical example, see How to Prove a Photo or Document Existed Before a Specific Date.
Main advantage: it is simple and familiar.
Main trade-off: the time evidence comes from the email system rather than a public blockchain.
A matching fingerprint shows that the file bytes match. The received email time shows when the ProofStamp reached that inbox.
nStamp
Best for a fast public blockchain timestamp
nStamp takes the same SHA-256 fingerprint and anchors it to the NEAR blockchain.
Instead of relying on an email record, you get an independently inspectable blockchain record with transaction and block details.
The original file does not need to be published. The public record contains the fingerprint.
Later, someone with the original file can calculate its SHA-256 again and compare it with the fingerprint recorded earlier.
Main advantage: a public blockchain record is available after the transaction confirms.
Main trade-off: it is a blockchain-specific workflow, which is more technical than email.
ProofStamp via Bitcoin
Best for a portable Bitcoin-backed timestamp
ProofStamp via Bitcoin uses OpenTimestamps.
The browser hashes your file locally and creates a standard .ots proof tied directly to that file’s SHA-256 fingerprint.
You keep the proof.
That portability is important. A completed proof is designed to remain independently verifiable even if ProofStamp.org is no longer available. Standard OpenTimestamps tools can verify it.
Bitcoin anchoring takes time
A newly created timestamp is not immediately Bitcoin-verified.
It starts in a Waiting for Bitcoin state.
You save the receipt and check again later. Once the Bitcoin attestation is available, the proof can support a narrow claim:
The matching file fingerprint existed no later than the verified Bitcoin anchoring block.
It does not turn the Bitcoin block time into the file’s original creation time.
Main advantage: a portable, open proof with a strong independent verification path.
Main trade-off: final Bitcoin anchoring is asynchronous.
Experimental
ProofStamp via Arbitrum
Best for exploring a smoother blockchain workflow
ProofStamp via Arbitrum explores a different approach.
The browser calculates the file’s SHA-256 locally and records the fingerprint as an Ethereum Attestation Service record on Arbitrum Sepolia.
The prototype uses passkeys instead of seed phrases and can sponsor the blockchain transaction, so a normal test user does not need to acquire testnet ETH first.
After the transaction, the application reads the attestation back from Arbitrum and checks it before reporting success.
This is useful because it demonstrates what a blockchain ProofStamp could feel like when the blockchain mechanics are pushed into the background.
But the status matters.
This is an Arbitrum Sepolia testnet reference implementation, not a production evidence service.
Main advantage: passkeys, sponsored transactions, and direct on-chain attestations make the workflow feel closer to a normal web app.
Main trade-off: testnet only.
Testnet prototype
The four options side by side
| nStamp | Bitcoin | Arbitrum | ||
|---|---|---|---|---|
| Good fit | Everyday evidence | Fast public timestamp | Portable long-term timestamp | Exploring blockchain UX |
| Original file uploaded by ProofStamp | No | No | No | No |
| Time evidence | Email received time when sent | NEAR block record | Bitcoin anchoring block | Arbitrum Sepolia block |
| Public blockchain | No | NEAR | Bitcoin | Arbitrum Sepolia testnet |
| What you keep | Plain-text ProofStamp | Transaction / proof record | Receipt + standard .ots | Receipt + EAS Proof ID |
| Independent check | Recalculate SHA-256 | Inspect public record | OpenTimestamps tools | Read EAS from Arbitrum |
| Current status | Ready to use | Ready to use | Experimental | Testnet prototype |
Which one is stronger?
It depends on what you need.
Imagine a contractor takes photos before starting work on someone’s property.
The important thing may simply be to create a record immediately and keep a copy in an inbox. Email ProofStamp is a good fit. That is the same idea behind Before You Leave the Job, ProofStamp the Photo.
Now imagine a document where a public timestamp matters. nStamp gives you a public blockchain record.
If you care more about keeping a standardized timestamp proof that can be verified independently years later, the Bitcoin and OpenTimestamps path has different advantages.
If you are building a product and want to see how passkeys and sponsored transactions could hide blockchain complexity from users, the Arbitrum prototype is the more relevant experiment.
The method should follow the job.
What all four start with
They all depend on the same basic tool: SHA-256.
SHA-256 turns the exact bytes of a file into a fixed-length digital fingerprint.
Give it the same bytes again and you get the same fingerprint.
Change even one byte and the fingerprint changes.
That lets you answer a useful question later:
Is this the same digital file that was recorded before?
If you want to understand the mechanism, read What Is a Hash Function? SHA-256 Explained.
What none of these methods proves
A timestamped fingerprint is evidence about a particular digital state.
- It does not automatically prove that the contents are true.
- It does not prove who created or owns the file.
- It does not prove when the file was originally created.
- It does not prove where a photo was taken.
- It does not prove that the file was never edited before it was stamped.
A false document can be stamped too.
That is why ProofStamp keeps the claim narrow: evidence of existence and integrity, not proof of truth.
Same fingerprint. Different proof.
Email favors simplicity.
nStamp gives you a fast public blockchain record.
Bitcoin and OpenTimestamps favor portability and independent verification.
Arbitrum explores what a smoother blockchain-based ProofStamp could look like.
You do not need to choose based on which technology sounds more impressive.
Choose based on the evidence you need.
Try ProofStamp
Choose the method that fits the job.
If you are looking at ProofStamp for approvals, inspections, handoffs, audit trails, or other company workflows, see ProofStamp for Business.