What is Postel's Law?

Be liberal in what you accept, conservative in what you send. Jon Postel's principle for TCP/IP protocol design enables interoperability between imperfect implementations.

Has Postel's Law caused problems?

Liberal HTML parsing enabled web compatibility but also normalized broken markup. Security researchers argue excessive liberality creates attack surfaces.

Postel's Law: Liberal/Conservative Robustness Principle

Formula Definitions

The Postel's Law: Liberal/Conservative Robustness Principle works by applying a well-defined formula to the values you enter. Understanding the formula behind the calculation helps you interpret the result and check that your inputs are correct. Below we break down the key components that drive the Postel's Law.

The core formula used by this calculator is:

Result = f(inputs, settings)

Each variable in the formula has a specific meaning:

inputs — Values entered into the Postel's Law.
settings — Options, units, or parameters that adjust how the calculation is performed.
Result — Computed output for the chosen inputs and settings.

How to Use This Calculator

Enter the required values. Enter the required values into the Postel's Law: Liberal/Conservative Robustness Principle input fields.
Adjust settings. Adjust any settings, select applicable options, or choose units as needed.
Calculate the result. Press Calculate to compute the result using the underlying formula.
Interpret the output. Review and interpret your result using the provided context, reference ranges, or explanatory notes.

Glossary and Definitions

Input: A value entered into the calculator to be processed.
Output: The computed result returned by the calculator for the given inputs.
Setting: An option that adjusts how the calculation is performed, such as unit selection or mode.
Postel's law: A key concept referenced by the Postel's Law: Apply Postel's Law (Robustness Principle) to system interface design. Calculate the tradeoff between liberal input acceptance and strict output formatting, and evaluate security vs interoperability implications.
Robustness principle: A key concept referenced by the Postel's Law: Apply Postel's Law (Robustness Principle) to system interface design. Calculate the tradeoff between liberal input acceptance and strict output formatting, and evaluate security vs interoperability implications.
Liberal input conservative output: A key concept referenced by the Postel's Law: Apply Postel's Law (Robustness Principle) to system interface design. Calculate the tradeoff between liberal input acceptance and strict output formatting, and evaluate security vs interoperability implications.
API design principle: A key concept referenced by the Postel's Law: Apply Postel's Law (Robustness Principle) to system interface design. Calculate the tradeoff between liberal input acceptance and strict output formatting, and evaluate security vs interoperability implications.

Related Calculators

Gall's Law

Miscellaneous Niche

Goodhart's Law