Being emotionally safe with a person enables people to loosen their grip and display more of themselves. It is a feeling of security that is gained over time by trust, respect and regularity of action. When people do not think they will be judged, dismissed, and criticized, their communication style, body language, and emotional expression will change in little and significant ways. These are usually slight and non-obvious changes that one would not notice unless he/she is keen to notice. They are comfortable, open, and reflective that the relationship is supportive. Although everyone might have their way of saying security, there are usually trends that are evident when one feels safe and comfortable in the presence of another person after some time.
They exchange subtle personal information

When the individuals feel secure, they start sharing daily thoughts, recollections or emotions that they may otherwise keep as secrets. These facts might be considered as normal, yet they demonstrate trust. Giving little slices of personal life are a sign of assurance and an understanding that you will listen to you and you will respond to you in an understanding manner instead of dismissing or judging you in the long run.
Their Body Language Softens

Emotional comfort is commonly displayed in physical posture. Shoulders are relaxed, arms uncrossed and movements more natural. They are not tense or guarded, but they look relaxed in the company. It is a light body language, which implies that they do not have to be defensive, which means that they are increasingly feeling emotionally safe and confident in the communication.
They Have Semi-Eye contact

Emotional ease is often indicated by comfortable eye contact, which is neither stiff nor avoidant. It is a manifestation of being there and trust. When one is able to look at you naturally as he or she speaks or listens you will find that the person feels safe to be viewed and is not afraid of being judged negatively or rejected at the given time.
They are Sincere in their Opinions

The security helps people to be able to express real thoughts, which may not match yours. They have faith that dispute will not hurt the relationship. This openness demonstrates confidence in the relationship and the confidence that their voice is appreciated instead of being condemned or and ignored.
They request you to take your point of view

When they ask your opinion, it is an indication that they care and trust your answer. It is that they feel free involving you in their decision-making or thoughts. This transparency is an indication of emotional safety and the feeling that your contribution will be treated carefully and with respect.
They Laugh More Freely

True laughter can be seen when a person is not stressed. Humor does not flow forcefully and they do not have to care about how they are going to sound or appear. This comfort implies that they do not feel like being out of place, and they do not have to be guarded or excessively controlled.
They Show Vulnerability

Venting concerns, insecurities, or emotional pain means trust. When a person shares personal things, then it means that they will answer you with a feeling that you will treat them with empathy and sympathy. One of the most obvious indicators of emotional protection is vulnerability.
They Like to Keep Things to Themselves

Ease is demonstrated by not being stressed to fill every pause. Cozy silence implies they are not afraid of embarrassment and rejection. It is just enough to be there and this is a sign of a serene and safe relationship.
They Have Biographical Knowledge of You

Remembering little things you have told is a sign of interest and concern. It shows emotional commitment and contentment with the relationship. Memorization of details is to bolster the trust and understanding between each other.
They Respect Boundaries

When a person feels secure, he or she tends to respect limits and express his or her. Trust is also demonstrated by mutual respect of boundaries and emotional security, which in turn helps to establish a sense of stability in the relationship.
They Keep Coming Back to Talk

To come with you again is a sign of easy-going. Coming back to talk implies that they will feel that you are there with their comprehension and emotional comfort, which will enhance the feeling of security they experience towards you.