Extension:Math/Unique Ids
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The attribute "id" is already live in all production Wikipedia systems. It allows linking to an individual equation that has the id attribute set.
For example the code
<math id="MassEnergyEquivalence">E=mc^2</math>
can be accessed via appending #MassEnergyEquivalence to the Page URL.
Visually no difference can be seen in the output
See for example kinetic Energy