RabbitMQ: maximum size of a message

What is the maximum size of a message in RabbitMQ?

The maximum size of a message in RabbitMQ is not defined by the protocol, but by the implementation. Unfortunately, this value is not well documented and has changed a lot over time, so we made this short article to summarize the current state of affairs.

RabbitMQ message size limits by version

• As of version 4.0, the maximum size of a message in RabbitMQ is 16 MiB (16,777,216 bytes). Checkout the GitHub thread.
• In version 3.9 and above, the default limit is 128 MiB (134,217,728 bytes). This limit can be bumped up to 512 MiB (536,870,912 bytes) by setting the max_message_size configuration option. See GitHub thread.
• Before that, the limit was set to 2 GiB (2,147,483,648 bytes).

What is the maximum number of characters in a message in RabbitMQ?

Typically, when encoding a string in UTF8, each ASCII character takes a single byte, so in version 4.0, the maximum number of characters in a message is 16,777,216 characters. However, some non-ASCII characters take more space, for instance accents or emojis. In this case, the maximum number of characters in a message can be lower since some characters take up more space.

IMPORTANT limitation of the management plugin

The RabbitMQ management plugin has a limitation that prevents it from displaying messages larger than 50,000 characters (messages are truncated). If you need to read / consume larger messages, you can use RabbitGUI instead, which does not have this limitation.