Verifying a spArxx.io Certificate
Received a spArxx.io certificate, receipt, or verification link as evidence, from an editor, attorney, publisher, or as a court official? This page is for you. It doesn't require a spArxx.io account, and it doesn't require trusting spArxx.io's word for it.
What the proof actually claims
A spArxx.io timestamp is cryptographic proof that a specific file, in exactly the form recorded, existed at a specific date and time. That fingerprint (a SHA-256 hash) is permanently anchored to the Polygon public blockchain, and not just stored in spArxx.io's database.
Functionally, the claim is narrow: this file existed, unaltered, at this recorded time. It does not establish authorship, ownership, or the truth of the file's contents.
What's cryptographically locked vs. what isn't
| Immutable, on-chain | Mutable, off-chain metadata |
|---|---|
| SHA-256 file fingerprint | Submitter's displayed name |
| Registration date/time | Claimed vs. anonymous account status |
| Network, contract, transaction ID | Case file name, original filename, MIME type |
The right-hand column can change after the fact (e.g. an account gets claimed under a real name later) without affecting the underlying proof at all. Only the left-hand column is what the blockchain actually guarantees.
Four ways to verify, in increasing order of independence from spArxx.io
None of these require a paid account.
1. The receipt (fastest)
Click the verify link. It returns the recorded data directly from spArxx.io. No account, no install needed.
2. The blockchain, directly
Every receipt links to the transaction on a public Polygon block explorer. An independent source, not controlled by spArxx.io. No account, no install needed.
3. The spArxx.io app's Verify tool (optional)
If you don't mind installing spArxx.io's free app, its Verify tab checks a dragged-in file against a known fingerprint instantly, with no manual hashing commands ... and it works anonymously, with no account or email required. The trade-off, stated plainly: this means trusting spArxx.io's own software to check correctly, and it does require an install. If you'd rather not use any spArxx.io software at all, options 2 and 4 don't require it either.
4. Fully independent verification (maximum independence from spArxx.io)
If you have the original file:
- Compute its SHA-256 hash yourself:
shasum -a 256 <file>(Mac/Linux) orcertutil -hashfile <file> SHA256(Windows). No file upload, no third-party tool needed. - Compare it to the "Digital Fingerprint" printed on the certificate, or shown on the receipt.
- Independently query the transaction on any public Polygon RPC/explorer of your choosing and confirm it recorded that same fingerprint.
This Option 4 never contacts spArxx.io's servers or software at all.
Privacy
spArxx.io does not attach any special tracking or analytics to certificate verification beyond standard web request logging. There is no bespoke "who checked this" record. If you need zero footprint regardless, use Option 4 above.
Programmatic / bulk verification
There's no fully open, no-account API for this today. In the meantime, an AI agent can verify certificates on your behalf via a free spArxx.io account. See: Agentic AI: Claude Code or Agentic AI: Custom Connector.