May 22, 2025•2 min read
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.
max_message_size
configuration option. See GitHub thread.Note that because a version supports a given message size limit does not mean that it is fine to approach it. In practice, it is recommended to keep messages small and way bellow the limit (a few MiB) to avoid performance issues and memory consumption problems. See how to reduce messages size bellow.
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.
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.
It usually not a good idea to send large messages in RabbitMQ, a simple way to reduce this is to store the payload in a database or an object storage service (like S3) and send a reference to it in the message, like an ID. This way, you can keep the message size small while still being able to access the full payload when needed.
This approach has the added benefit of allowing you to store large payloads in a more efficient way, as databases and object storage services are designed to handle large files and can provide better performance and scalability.
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