As a changeling, you have the following racial traits.
Ability Score Adjustment. Your Charisma score increases by 2 and your Dexterity score increases by 1.
Age. Like humans, changelings reach adulthood in their late teens and live less than a century.
Alignment. Changelings of all alignments exist, but most gravitate toward the neutral alignment. They focus on their own concerns without any meaningful regard for laws or morals. Many have their own code of honor but are also fiercely independent. Some refuse to engage in assassination, while others embrace that path as the most perfect form of the changeling art of deception.
Size. Changelings in their native form fall within the boundaries of Medium size, usually standing between 5 and 6 feet tall.
Speed. Your base walking speed is 30 feet.
Shapechanger. You can use an action to polymorph into a Small or Medium humanoid you have seen, or back into your true form. Your statistics, other than your size, are the same in each form. Any equipment you are wearing or carrying isn’t transformed. You revert to your true form if you die. Any creature that attempts to see through your ruse may make a Wisdom (Insight) check opposed by your Charisma (Deception) check.
Natural Linguist. Learning a new language takes half the amount of downtime that it normally takes.
Skill Proficiency. You have training in the Deception and Insight skills.
Slippery Mind. You have advantage on saving throws against being charmed.
Languages. You can speak, read, and write Common and one extra language of your choice. Common allows you to move easily among humans and members of all other races. Many changelings learn as many other languages as they can to facilitate a multitude of disguises.