"Is up to" is a popular phrase that can be easily replaced by several synonyms. Some of the commonly used alternatives for this phrase include "is dependent on," "is in the hands of," "is at the discretion of," "is determined by," or "is decided by." Each of these synonyms emphasizes the idea that the outcome of a situation is subject to certain factors or conditions, whether they are controlled by an individual or external circumstances. By using these synonyms, writers or speakers can add variety to their language and avoid repetition. Moreover, these synonyms can help to more precisely convey the intended meaning and tone of a message.