E621 is a food additive that’s used to “enhance” the flavor of many common products such as chips, soups, crackers, etc, and while many of those products may not be vegan, it’s not the E621 that makes them non-vegan.
E621 is just a code-word for Monosodium Glutamate, aka MSG.
Regardless of what you want to call it E621/MSG is 100% Vegan, there are tons of ways it’s produced, all of which are 100% free of animal products and cruelty. E621 is definitely vegan.
Is E621 safe to consume?
There’s some controversy over whether or not it’s okay to eat E621, as there’s been tons of propaganda against MSG (E621) throughout the recent century in western countries. That propaganda is largely nonsense that was pushed by media who wanted a hysteric story to publish, and a number of anti-immigrant groups who didn’t like Chinese people opening so many restaurants many decades ago.
In reality E621 is completely safe if used normally (in food, not injected into your vein or some nonsense), and there’s really no issue with it at all. It’s much more potent than table salt, while at the same time being way lower in sodium, so it’s advisable to use it in the place of sodium on snack foods or in foods you may add salt to (pasta sauce for example).