Every snowflake is unique, or at least as best as we can figure out. It's probably true that no two snowflakes are alike, but the sheer number of snowflakes makes it virtually impossible to determine with certainty.
Who Ever Said No Two Snowflakes Were Alike? - The New York Times
No Two Snowflakes the Same Likely True, Research Reveals
14 fascinating physics facts about flakes (of snow)
Wilson Bentley Quote: “No two snowflakes are alike”
How do scientists know that 'no two snowflakes are alike' when all the snowflake haven't been compared with each other? - Quora
No Two Snowflakes the Same Likely True, Research Reveals
Is it true that no two snowflakes are identical? Office for Science and Society - McGill University
How do scientists know that 'no two snowflakes are alike' when all the snowflake haven't been compared with each other? - Quora
The Science Behind Why No Two Snowflakes Are Alike