# 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:
1. Compute its SHA-256 hash yourself: `shasum -a 256 <file>` (Mac/Linux) or `certutil
   -hashfile <file> SHA256` (Windows). No file upload, no third-party tool needed.
2. Compare it to the "Digital Fingerprint" printed on the certificate, or shown on the
   receipt.
3. 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](/agentic-ai/claude-code) or
[Agentic AI: Custom Connector](/agentic-ai/custom-connector).