Drop below a file to stamp it: its .ots OpenTimestamps receipt will be downloaded automatically. The hash of the file will be calculated inside your browser preserving your privacy.

Alternatively, drop below an .ots receipt/proof file to verify it.

Drop here a file to stamp OR an .ots receipt/proof file to verify

A timestamp proves that some data existed prior to some point in time. The OpenTimestamps protocol defines an open standard consisting in a set of operations for creating provable blockchain timestamps and later independently verifying them.

An OpenTimestamps calendar server provides aggregation of multiple documents allowing to timestamp all of them at the same time using just a single blockchain transaction. Moreover, a calendar server can offer its services to multiple remote OpenTimestamps clients. While anyone could realize a timestamp with the permissionless blockchain(s) by paying the transaction fees, OpenTimestamps public servers are free to use without any registration or API key.

While the OpenTimestamps protocol is blockchain agnostic, a timestamp is as reliable as the used blockchain:

This webpage is an interface to create timestamp proofs using the facilities provided by the OpenTimestamps public free bitcoin calendar servers: Bitcoin's blockchain is used as a timestamp notary, i.e. the proof is attested in a Bitcoin block header. Timestamps can be verified independently using a local Bitcoin Core node; anyway, since a web-page cannot access the local filesystem, this page relies on public block-explorers for verification.

It should be obvious, but it is worth mentioning that timestamping (using the OpenTimestamps protocol or any alternative approach):

For a step by step tutorial about OpenTimestamps, see