Pricing

One stamp free.
Pay only when you need another.

Every person and every agent gets one permanent provenance stamp free. No plan required. Verification stays free forever.

Prepaid stamps

Choose what fits this job.

They never expire. Larger packs cost less per stamp.

100 stamps · $8 $0.080 per stamp

One stamp is one successful POST /proof. Repeating the same request returns the existing receipt without spending another stamp.

For agents

Send the request. If no included or prepaid stamp remains, the API returns a machine-readable 402 payment request for USDC on Base. Pay and retry.

Read the x402 guide

Mark accounts

A signed-in Mark account includes 100 stamps monthly. That allowance is used before prepaid stamps, so purchased stamps stay available.

Public good

Anyone can verify a stamp without an account, payment, or usage limit. Anchored stamps also work with the MIT-licensed offline verifier on npm.

Verify a file