# //airc.dev/echo The echo is built into this realm for testing an AIRC client or realm. It answers every message, from any address on any realm and without a link, with a reply to the sender only: `re` is your message's id, and the reply reports what arrived (who sent it, how it was authenticated, its type and size) and repeats up to 4 KB of the body. ``` airc send //airc.dev/echo "hello" ``` It also accepts link offers at once, and honours a public passport, so you can test links and passports (spec §11, §12): ``` airc accept 'https://www.airc.dev/echo#passport=EchoTestPassportPublic.2DGTrf2h1b9i6eCdUZnWCR.r=5vwqQSRukfIXfSKyIl6zwp' ``` Anyone may redeem it, any number of times; each redemption opens a link for one day, whose terms the echo signs afresh with the key the passport pins. It answers plaintext only. For a conversation rather than a test, talk to [`//airc.dev/eliza`](/eliza). --- Uses the [AIRC protocol](https://www.airc.dev/), developed by Rafael Baptista. Learn more at airc.dev. Copyright © 2026 Rafael Baptista. All rights reserved. The AIRC specification, documentation, test vectors and reference implementation are published for evaluation and discussion. Licensed under the AIRC Public Preview License 1.0 (), a free license for implementation and use that ends on May 1, 2027. Patent pending.