What is the Zcash memo field?

A field of 512 bytes that can be attached to a payment sent to a shielded receiver. It is encrypted, so only the recipient and anyone holding the relevant viewing key can read it. People use it for invoice numbers, order references or short messages.

How long can a Zcash memo be?

512 bytes. For plain English text that is roughly 512 characters, but characters outside basic ASCII, such as accented letters, non-Latin scripts and emoji, take two to four bytes each in UTF-8, so the visible character count is lower.

Who can read a Zcash memo?

The recipient, and anyone who has the recipient's viewing key. For a memo you sent, a full viewing key of your own account can also show it when the transaction was built in the standard way. The public blockchain shows nothing readable.

Do transparent Zcash addresses support memos?

No. Only shielded receivers (Sapling, Orchard and Ironwood) carry the encrypted memo field. A payment to a transparent address or to the transparent receiver of a Unified Address cannot include a memo.

ZIP 302 is a Draft standard for how the 512 bytes are interpreted. A first byte of 0xF4 or lower means UTF-8 text padded with zeros, 0xF6 followed by zeros means no memo, and 0xFF means arbitrary data. Other values are reserved or ambiguous.

Is a Zcash memo really private?

It is encrypted on the blockchain, but it is not secret from the recipient's wallet, backups or anyone they share a viewing key with. Do not put passwords, seed phrases or other secrets in a memo.

Why does an exchange or service ask for a memo?

Some services use the memo as a reference to match a deposit to your account. If one asks for it, copy the exact text it gives you and send to its shielded address. A deposit to a transparent address cannot carry a memo.

Zcash Memo Field: Encrypted Messages Explained

Q: Does a memo cost extra in Zcash?

Not under the active ZIP 317 fee rules, where the fee depends on logical actions rather than memo content. A Draft Revision 2 would charge for memo chunks beyond two free ones, but it depends on an undeployed ZIP and does not apply today.

The Zcash memo field is an encrypted 512-byte message that can travel with a payment to a shielded address. Only the recipient, and anyone with the recipient's viewing key, can read it; the public blockchain shows nothing. People use it for invoice references, order numbers or short notes. Transparent addresses have no memo field.

This guide covers who can read a memo, what fits in 512 bytes, the draft format standard, and the limits you should know about before relying on it.

How the Zcash memo field works

When you pay a shielded receiver, the wallet encrypts the payment details together with the memo to the recipient's keys. The memo is part of that encrypted note, so the transaction on the blockchain looks the same whether or not you attached text. The size is fixed at 512 bytes. The field is always present on a shielded output; if you add nothing, the wallet fills it with the standard "empty" pattern.

Payments to a Unified Address can carry a memo only when they go to its shielded receiver. If the sender's wallet uses the address's transparent receiver instead, the memo cannot be included.

Who can read a memo?

The recipient. Their wallet decrypts it with the incoming viewing key it already holds.
Anyone with the recipient's viewing key. Our viewing key guide explains the difference between incoming and full keys. Sharing one reveals the memos of everything the account received.
You, the sender, in the standard case. A full viewing key of your own account can show the memo of an outgoing payment when your wallet built the transaction in the standard way.
Not the public. On the chain the memo is encrypted data.

The memo is private in transit and on the blockchain, but not secret from people at either end. Do not put passwords, seed phrases or other secrets in it, and remember that your wallet or its backups may keep a copy.

How many characters fit in 512 bytes?

The limit is in bytes, not characters. Plain English text uses about one byte per character, so roughly 512 characters fit. Accented letters usually need two bytes, characters from many other scripts need three, and emoji need four, so a message full of those is shorter.

The memo format: ZIP 302

ZIP 302, "Standardized Memo Field Format", defines how wallets interpret the 512 bytes. It is a Draft standard (owner Jack Grigg, original author Jay Graber) and the reference for how memos are formatted:

First byte	Meaning
`0xF4` or lower	A UTF-8 text message, padded with zero bytes to 512 bytes; readers strip the trailing zeros
`0xF5`	Ambiguously used in the past under private agreements; readers should make no assumptions
`0xF6` followed by all zeros	No memo; the field is treated as empty
`0xF7` to `0xFE`	Reserved for future versions of the format
`0xFF`	Arbitrary data; senders with private or non-standard data should use this value

For you this means a normal typed message is stored as padded UTF-8 text, a payment with no memo carries the "empty" marker, and applications that exchange structured data use the 0xFF form.

Why transparent addresses have no memo

The memo lives inside the encrypted note of a shielded output. A transparent output is just an amount and a script on the public chain, with no encrypted payload to hold text. That is why a deposit to a transparent address, including a TEX address, cannot carry a memo. See shielded vs transparent transactions for the full difference.

Do memos cost extra?

Under the active ZIP 317 Revision 0, no: the fee depends on logical actions, not on memo content. A Draft Revision 2 would charge for memo chunks beyond two free ones, but it depends on a ZIP that is not deployed. Details are in our transaction fees guide.

Practical tips

Copy memo requirements exactly. If a service gives you a reference text, paste it unchanged and send to the shielded address it provides.
Keep it short and non-sensitive. A reference number is ideal; secrets are not.
Check your wallet. Wallets differ in how they show and send memos. Confirm in your wallet's release notes before relying on it for payments.
Use the glossary. The memo field glossary entry has a one-line definition.

Sources and methodology

Checked on October 10, 2026 against ZIP 302: Standardized Memo Field Format (Draft), ZIP 317 for fees (Revision 0 Active) and the Zcash Protocol Specification for the 512-byte memo in shielded notes. Wallet display behaviour varies by app and version and was not tested here. New articles first appear in the ZecZcash Telegram channel.

Zcash Memo Field Explained: Encrypted Messages in Shielded Payments