> For the complete documentation index, see [llms.txt](https://www.designreference.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.designreference.xyz/cognitive-tools/ux-laws-principles/foundations/postels-law.md).

# Postel's Law

{% hint style="info" %}
AKA The Robustness Principle
{% endhint %}

Postel's Law is a guideline for designing computer network protocols. In simple terms, it suggests that when you send data over the internet, you should be liberal in what you accept and conservative in what you send.

1. "Be liberal in what you accept" means that when your computer receives data from the internet, it should try to understand and work with that data even if it's not perfectly formatted. It's like being open to different accents when you're listening to someone speaking English.
2. "Be conservative in what you send" means that when your computer sends data out, it should make sure that the data is well-structured and follows the rules precisely. It's like speaking clearly and following proper grammar when you're talking to someone.

This principle helps ensure that computer systems can communicate with each other even if they don't use exactly the same standards. It promotes flexibility and compatibility in the world of computer networks.

#### Further Reading

{% embed url="<https://lawsofux.com/postels-law/>" %}

{% embed url="<https://medium.com/kubo/postels-law-designing-for-robustness-1503ff1f72dd>" %}

{% embed url="<https://medium.com/perpetual/ux-design-principle-005-postels-law-d1ebac4e13d9>" %}

#### Further Viewing

{% embed url="<https://www.youtube.com/watch?v=e2cLZkSFpoU>" %}


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