After some reseach, I found out that length limits for names are 255 and for values 32767 characters.
But which characters are allowed for names?
And which characters are allowed for values?
What are valid characters for Windows environment variable names and values?
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3 Answers
It seems that the only prohibited character is equal ("=") sign - from https://docs.microsoft.com/en-us/windows/win32/procthread/environment-variables:
The name of an environment variable cannot include an equal sign (=).
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